JP2013003549A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module contrived to reduce damage of a light-emitting element caused by a stress with heat generation and to prevent an occurrence of peeling of a mirror part and an internal waveguide in a clearance part.SOLUTION: The optical module includes: an internal waveguide 16 provided in a groove 1a that is formed on the surface of a substrate 1; and a mirror part 15 for optical path conversion formed at the tip end of the groove 1a. The optical module includes at least optical elements 12a and 12b that are mounted on the surface of the substrate 1 so as to face the mirror part 15, and emit an optical signal to a core part 17 of the internal waveguide 16 via the mirror part 15 or receive an optical signal from the core part 17 of the internal waveguide 16 via the mirror part 15. A material of the internal waveguide 16 of a clearance part S between the optical element 12a out of the optical elements 12a and 12b and the mirror part 15 is a low-stress material different from the material of the other part of the internal waveguide 16.

Description

  The present invention relates to an optical module including an optical element.

  2. Description of the Related Art Conventionally, an optical module includes an internal waveguide provided in a groove formed on the surface of a substrate, and an optical path conversion mirror part formed at the tip of the groove. Also, it is mounted on the surface of the substrate so as to face this mirror part, and emits an optical signal to the core part of the internal waveguide through the mirror part, or light from the core part of the internal waveguide through the mirror part. Some include at least an optical element that receives a signal (see Patent Document 1).

  Here, the core part and the clad part of the internal waveguide are made of synthetic resin, and the mirror part is made of metal such as gold plating. Further, the core portion of the internal waveguide extends just before the gap portion between the optical element and the mirror portion, and this gap portion is filled with the same material as that of the cladding portion.

  By the way, when the optical module is operating, the metallic mirror part and the synthetic resin internal waveguide in the gap may generate heat due to light absorption. In particular, when the optical element is a light-emitting element, the vicinity of the mirror portion close to this is before the light spreads, and thus the light power density is high, so that the heat generation temperature tends to increase.

  In such an optical module, if the transmission distance is short or low, the power density of the light from the light emitting element is low, so that the heat generation temperature of the internal waveguide in the mirror part or the gap part does not become so high as to be a problem.

JP 2009-260227 A

  However, in the case of long distance and high-speed transmission, higher light output is required to ensure transmission reliability, and the heat generation temperature of the internal waveguide in the mirror part and the gap part increases accordingly.

  Therefore, there is a possibility that the light emitting element may be damaged due to the stress generated by the temperature rise of the internal waveguide in the mirror part or the gap part, or the internal waveguide in the mirror part or the gap part may be peeled off.

  Here, the internal waveguide of the gap portion is for improving the optical coupling efficiency, but as long as it is limited to a short distance of the gap portion between the light emitting element and the mirror portion, even if there is no internal waveguide, The decrease in optical coupling efficiency is considered slight.

  Therefore, considering the reliability and lifetime of the entire optical module, the gap between the optical element and the mirror should be made of a material that is less stressful with respect to temperature rise than a material with excellent optical coupling efficiency. Would be desirable.

  The present invention has been made on the basis of the above-described knowledge, and has been devised so as to reduce the damage of the light emitting element due to the stress caused by heat generation and to prevent the internal waveguide of the mirror part and the gap part from being peeled off. It is an object to provide an optical module.

  In order to solve the above-described problems, the present invention provides an internal waveguide provided in a groove formed on the surface of a substrate, an optical path conversion mirror formed at the tip of the groove, and the mirror Light that is mounted on the surface of the substrate so as to face the substrate and emits an optical signal to the core portion of the internal waveguide via the mirror portion, or receives an optical signal from the core portion of the internal waveguide via the mirror portion In the optical module including at least an element, the material of the internal waveguide in the gap portion between the light emitting element and the mirror portion in the optical element is lower in stress than the material of the other internal waveguide. An optical module characterized by being made of another material is provided.

  In the groove of the substrate, the internal waveguide other than the gap portion is formed in advance, and the gap waveguide portion is filled with the low stress different material, so that the internal waveguide of the gap portion is formed. It can be set as a structure.

  In the groove of the substrate, the internal waveguide other than the gap portion is formed in advance, and the gap portion is filled between the optical element and the surface of the substrate. It can be set as the structure by which the internal waveguide of a clearance gap part is formed by being filled with a certain sealing material simultaneously.

  According to the present invention, the material of the internal waveguide in the gap portion between the light emitting element and the mirror portion in the optical element is made of another material having a lower stress than the other internal waveguide materials. .

  Therefore, even if the heat generation temperature of the mirror part or the gap part between the optical element and the mirror part becomes high, the gap part is a different material with low stress, so that damage to the light emitting element due to the stress is reduced. In addition, peeling is unlikely to occur in the internal waveguides in the mirror part and the gap part.

1 is a schematic side view of an optical module according to the present invention. It is the 1st board | substrate of the optical module of the light emission side of FIG. 1, (a) is side surface sectional drawing, (b) is II sectional view taken on the line of (a), (c) is II-II line of (a). It is sectional drawing. 2A is a perspective view of the first substrate of FIG. 2, and FIG. 3B is a perspective view in which an internal waveguide is formed. FIG. 3A is a perspective view in which a light emitting element is mounted, and FIG. 3B is a perspective view in which an optical fiber is inserted. (A) is the perspective view which fixed the pressing block to the 1st board | substrate, (b) is the perspective view of an optical fiber. (A) is side surface sectional drawing of the 1st board | substrate of 1st Embodiment, (b) is side surface sectional drawing of the 1st board | substrate of 2nd Embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic side view of an optical module according to the present invention. 2 is a first substrate 1 of the light-emitting side optical module of FIG. 1, (a) is a side sectional view, (b) is a sectional view taken along line II of (a), and (c) is a sectional view of (a). It is II-II sectional view taken on the line.

  3A and 3B show the first substrate 1. FIG. 3A is a perspective view, and FIG. 3B is a perspective view in which an internal waveguide 16 is formed. 4A and 4B show the first substrate 1, in which FIG. 4A is a perspective view in which the light emitting element 12a is mounted, and FIG. 4B is a perspective view in which the optical fiber 2 is inserted.

  FIG. 5A is a perspective view in which the holding block 24 is fixed, and FIG. 5B is a perspective view of the optical fiber 2.

  In FIG. 1, an optical module (optical module) optically couples a first substrate (mount substrate) 1 on a light emitting side, a first (mount) substrate 3 on a light receiving side, and the first substrates 1 and 3. And an optical fiber 2.

  The first substrates 1 and 3 need to have rigidity in order to avoid the influence of heat during mounting and the influence of stress due to the use environment. Further, in the case of optical transmission, since optical coupling efficiency from the light emitting element 12a to the light receiving element 12b is required, the optical elements (the light emitting element 12a and the light receiving element 12b) can be mounted with high accuracy and the positional fluctuation during use. Must be suppressed as much as possible. For this reason, a silicon (Si) substrate is employed as the first substrates 1 and 3 in this embodiment.

  In particular, in the case of a silicon substrate, it is possible to process a highly accurate etching groove on the surface by utilizing the crystal orientation of silicon [a highly accurate mirror portion 15 (described later) using this groove, and an internal waveguide 16 ( (To be described later). ]. In addition, the silicon substrate has good flatness.

  The first substrates 1 and 3 are respectively installed on the surface (upper surface) of a second substrate (interposer substrate) 6 having a larger size. Connectors 7 for electrically connecting to other circuit devices are respectively attached to the back surface (lower surface) of each second substrate 6.

  On the surface (upper surface) of the first substrate 1, a light emitting element 12a that converts an electrical signal into an optical signal is flip-chip mounted with bumps 12c (see FIG. 2) with the light emitting surface facing downward. An IC substrate (signal processing unit) 4a on which an IC circuit for transmitting an electrical signal to the light emitting element 12a is formed is mounted on the surface of the second substrate 6.

  In the present embodiment, a surface emitting laser (VCSEL (Vertical Cavity Surface Emitting Laser)) that is a semiconductor laser is employed as the light emitting element 12a. The light emitting element 12a may be an LED or the like.

  The IC substrate 4a is a driver IC that drives the VCSEL, and is disposed in the vicinity of the light emitting element 12a. The light emitting element 12a and the IC substrate 4a are connected to a metal circuit (patterning circuit by copper or gold sputtering) formed on the surface of the first substrate 1.

  On the surface of the first substrate 1, as shown in FIG. 3 (a), a substantially trapezoidal first groove (waveguide forming groove) 1a and a substantially V-shaped second deeper than the first groove 1a. The groove 1b is formed continuously in the front-rear direction.

  At the tip of the first groove 1a, an optical path changing mirror 15 for bending the optical path by 90 degrees is formed at a position directly below the light emitting element 12a. The mirror portion 15 is subjected to gold plating for improving the reflectance.

  As shown in FIG. 3B, an internal waveguide 16 that is optically coupled to the light emitting element 12a of the first substrate 1 is provided in the first groove 1a of the first substrate 1. The internal waveguide 16 extends from the mirror portion 15 in the direction of the second groove 1b and is flush with the rear end portion 1d of the first groove 1a.

  The internal waveguide 16 includes a core portion 17 having a substantially square cross section with a high refractive index through which light propagates, and a cladding portion 18 having a refractive index lower than that. As shown in FIG. 2C, the left and right surfaces of the core portion 17 are covered with the cladding portion 18.

  As shown in FIG. 4A, a light emitting element 12a is mounted at a predetermined position on the surface of the first substrate 1 where the internal waveguide 16 is provided, and between the light emitting element 12a and the surface of the first substrate 1. As shown in FIG. 2A, an optical transparent resin (sealing member: underfill material) 13 is filled.

  Returning to FIG. 1, the first substrate 3 on the light receiving side will be described. The basic structure of the first substrate 3 on the light receiving side is the same as that of the first substrate 1 on the light emitting side. However, on the surface (upper surface) of the first substrate 3 on the light receiving side, a light receiving element 12b for converting an optical signal into an electric signal is flip-chip mounted with bumps with the light receiving surface facing downward. In addition, on the surface of the second substrate 6, an IC substrate (signal processing unit) 4b on which an IC circuit for transmitting an electric signal to the light receiving element 12b is formed is mounted. Different from 1. As this light receiving element 12b, PD (Photo Diode) is adopted, and the IC substrate 4b is an element such as a TIA (Trans-impedance Amplifier) that performs current / voltage conversion.

  The first substrate 1 on the light emitting side, the first substrate 3 on the light receiving side, and the IC substrates 4 a and 4 b are shielded by a shield case 8 attached to the surface of the second substrate 6, respectively. The through hole 8a is penetrated.

  Next, the optical fiber 2 will be described. As shown in FIGS. 1 and 5, the optical fiber 2 includes a core portion 17 of the internal waveguide 16 of the first substrate 1 on the light emitting side and a core portion 17 of the internal waveguide 16 of the first substrate 3 on the light receiving side. An optically connectable fiber core portion 21 is provided inside. And it is a cord type comprised by the fiber cladding part 22 surrounding the outer periphery of this fiber core part 21, and the coating | coated part 23 which coat | covers the outer periphery of this fiber cladding part 22. FIG. The fiber core portion 21, the fiber clad portion 22, and the covering portion 23 are circular.

  As shown in FIG. 1, the optical fiber 2 penetrates the through hole 8a of the shield case 8 and the covering portion 23 is peeled off in the vicinity of the second groove 1b of the first substrate 1 so that the fiber clad portion 22 is exposed. Yes.

  Then, as shown in FIGS. 2A, 2C, and 4B, the fiber clad portion 22 of the optical fiber 2 is installed in the second groove 1b of the first substrate 1, and the boundary portion with the first groove 1a. The fiber clad portion 22 is positioned at the rising slope portion. At this time, it is optically coupled with the optical axis of the core part 17 of the internal waveguide 16 of the first substrate 1 and the fiber core part 21 of the optical fiber 2 being aligned.

  At the position of the surface of the first substrate 1, as shown in FIGS. 2A and 5, a holding block 24 is disposed on the upper portion of the fiber cladding portion 22 of the optical fiber 2, and the holding block 24 and the second groove 1 b are arranged. The space between is filled with the adhesive 14.

  As described above, the front end side of the fiber clad portion 22 of the optical fiber 2 is bonded and fixed to the first substrate 1 together with the pressing block 24 with the adhesive 14 while being pressed against the second groove 1 b by the pressing block 24. become.

  FIG. 6A is a side cross-sectional view of the first substrate 1 of the first embodiment in which heat generation measures are taken. The material of the cladding portion 18 ′ of the internal waveguide 16 in the gap portion (substantially triangular portion in side view) S between the light emitting element 12 a and the mirror portion 15 is less stressed than the materials of the other cladding portions 18. It is a material.

  The material of the clad portion 18 ′ of the gap portion S can be, for example, a urethane rubber-based or silicon rubber-based resin.

  In the first embodiment, the material of the cladding portion 18 ′ of the internal waveguide 16 in the gap portion S between the light emitting element 12 a and the mirror portion 15 is lower than the material of the cladding portion 18 of the other internal waveguide 16. It is a separate material with stress.

  Therefore, even if the heat generation temperature of the mirror portion 15 or the gap portion S between the light emitting element 12a and the mirror portion 15 becomes high, the gap portion S has low stress (low αE α is linear expansion coefficient E is elastic modulus). Since it is a different material, damage to the light emitting element 12a due to stress is reduced, and peeling is less likely to occur in the mirror portion 15 and the clad portion 18 'of the internal waveguide 16 in the gap portion S.

  In the first embodiment, the internal waveguide 16 other than the gap portion S is formed in advance in the first groove 1 a of the first substrate 1. Thereafter, the gap portion S is filled with another low-stress material that is the material of the clad portion 18 ′, whereby the clad portion 18 ′ of the internal waveguide 16 can be formed in the gap portion S.

  Thus, by forming the internal waveguide 16 in advance, it is possible to minimize the clad portion 18 'of the internal waveguide in the gap portion S where patterning cannot be performed. That is, if the cladding portion 18 ′ of the internal waveguide 16 in the gap portion S is formed first, the ultraviolet light for patterning exposure is reflected by the mirror portion 15, so that the other leaked to the other internal waveguide 16 side. This is because the clad portion 18 ′ of the internal waveguide 16 made of another material may be formed in the region of the other internal waveguide 16 depending on the material.

  FIG. 6B is a side cross-sectional view of the first substrate 1 of the second embodiment in which measures against heat generation are taken. The difference from the first embodiment is that the step of filling the gap portion S with another low-stress material that is the material of the cladding portion 18 ′ is omitted.

  That is, as described with reference to FIG. 2A, an optical transparent resin (sealing member: underfill material) 13 is filled between the light emitting element 12 a and the surface of the first substrate 1. As the sealing material, the optical transparent resin 13 is usually made of a low stress material in order to reduce the influence of stress on the light emitting element 12a. It is possible to use both.

  Therefore, the optical transparent resin 13 is filled between the light emitting element 12 a and the surface of the first substrate 1, and at the same time, the optical transparent resin 13 is filled in the gap portion S, whereby the internal waveguide 16 is filled in the gap portion S. The clad portion 18 'is formed.

  Thus, in the step of filling the light transparent element (sealing member) 13, which is another low stress material, between the light emitting element 12 a and the surface of the first substrate 1, the optical transparent resin ( Since the sealing member 13, that is, the clad portion 18 ′ can be filled at the same time, the step of filling another material becomes unnecessary.

  As described above, the optical module according to the present invention includes the internal waveguide provided in the groove formed on the surface of the substrate, the optical path conversion mirror formed at the tip of the groove, and the mirror. Mounted on the surface of the substrate so as to face the part, emits an optical signal to the core part of the internal waveguide via the mirror part, or receives an optical signal from the core part of the internal waveguide via the mirror part In an optical module including at least an optical element, the material of the internal waveguide in the gap portion between the light emitting element and the mirror part in the optical element is lower in stress than the material of the other internal waveguides. It is characterized by being a different material.

  According to this, the material of the internal waveguide in the gap portion between the light emitting element and the mirror portion in the optical element is a different material having a lower stress than the other internal waveguide materials.

  Therefore, even if the heat generation temperature of the mirror part or the gap part between the optical element and the mirror part becomes high, the gap part is a different material with low stress, so that damage to the light emitting element due to the stress is reduced. In addition, peeling is unlikely to occur in the internal waveguides in the mirror part and the gap part.

  In the groove of the substrate, the internal waveguide other than the gap portion is formed in advance, and the gap waveguide portion is filled with the low stress different material, so that the internal waveguide of the gap portion is formed. It can be done.

  According to this, by forming the internal waveguide in advance, it is possible to minimize the internal waveguide in the gap portion where patterning cannot be performed. In other words, if the internal waveguide in the gap is first formed, the ultraviolet light for patterning exposure is reflected by the mirror part, so that other internal waveguide leaks due to another material leaking to the other internal waveguide side. This is because an internal waveguide made of a different material may be formed in this region.

  In the groove of the substrate, the internal waveguide other than the gap portion is formed in advance, and the gap portion is filled between the optical element and the surface of the substrate. It can be set as the structure by which the internal waveguide of a clearance gap part is formed by being filled with a certain sealing material simultaneously.

  According to this, in the step of filling the sealing material (underfill material) which is another low-stress material between the optical element and the surface of the substrate, the gap material can be filled with the sealing material at the same time. Therefore, the step of filling another material becomes unnecessary.

1 1st board | substrate 1a 1st groove | channel 12a Light emitting element (optical element)
12b Light receiving element (optical element)
13 Optical transparent resin (sealing member: underfill material)
15 Mirror part 16 Internal waveguide 17 Core part 18 Clad part 18 'Clad part S Crevice part

Claims (3)

An internal waveguide provided in a groove formed on the surface of the substrate, an optical path conversion mirror formed at the tip of the groove, and mounted on the surface of the substrate so as to face the mirror, In an optical module including at least an optical element that emits an optical signal to the core portion of the internal waveguide via the mirror portion or receives an optical signal from the core portion of the internal waveguide via the mirror portion,
The material of the internal waveguide in the gap portion between the light emitting element and the mirror part in the optical element is another material having a lower stress than the material of the other internal waveguide. module.   In the groove of the substrate, the internal waveguide other than the gap portion is formed in advance, and the gap waveguide portion is filled with the low stress different material, so that the internal waveguide of the gap portion is formed. The optical module according to claim 1.   In the groove of the substrate, the internal waveguide other than the gap portion is formed in advance, and the gap portion is filled between the optical element and the surface of the substrate. The optical module according to claim 1, wherein an internal waveguide in a gap portion is formed by simultaneously filling a certain sealing material.

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