JP2015222291A - Baseplate structure and baseplate for optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a baseplate structure and a baseplate for optical module capable of improving the yield rate by forming a resin structure which is hardly peeled off from a baseplate by making measures against stress due to influence of mounting heat and application environment.SOLUTION: The baseplate structure includes: a baseplate 1; and a resin structure formed on the baseplate 1. The baseplate 1 has a stress relaxation structure 26 for easing a stress applied to the resin structure. The resin structure is a waveguide 16. The stress relaxation structure 26 is formed on at least one side of the waveguide 16. The stress relaxation structure 26 has a concave or convex shape. The stress relaxation structure 26 is formed on the surface of the baseplate 1.

Description

  The present invention relates to a substrate structure and an optical module substrate.

  Conventionally, as shown in FIG. 9A, the optical module includes an internal waveguide (resin structure) 16 provided in a first groove (waveguide forming groove) 1a formed on the surface of the substrate 1, And an optical path changing mirror portion 15 formed on the front end surface of the first groove 1a. Further, the optical element 12 is provided that emits an optical signal to the core portion 17 of the internal waveguide 16 via the mirror portion 15 or receives an optical signal from the core portion 17 of the internal waveguide 16 via the mirror portion 15. ing.

  Furthermore, an optical fiber (external waveguide) 2 having a fiber core portion 21 provided in the second groove 1b formed on the surface of the substrate 1 and optically coupled to the core portion 17 of the internal waveguide 16 is provided. (See Patent Document 1).

  By the way, when the optical module is operating, the mirror portion 15 and the synthetic resin internal waveguide 16 may generate heat due to light absorption. In particular, when the optical element 12 is a light-emitting element, the vicinity of the mirror portion 15 near this is before the light spreads, and thus the heat density tends to increase because the light power density is high.

  In such an optical module, if the transmission distance is short or low, the power density of the light from the optical element 12 is low, so that the heat generation temperature of the mirror portion 15 and the internal waveguide 16 in the vicinity thereof is so high as to be a problem. Don't be. 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 mirror unit 15 and the internal waveguide 16 in the vicinity thereof is increased accordingly.

  Therefore, there is a possibility that the core portion 17 is peeled off from the substrate 1 due to the stress caused by the temperature rise of the mirror portion 15 and the internal waveguide 16 in the vicinity thereof.

  Therefore, as shown in FIG. 9B, a device has been proposed in which the front end 17a of the core portion 17 is retracted from the mirror portion 15 to suppress the temperature rise so that peeling does not easily occur.

JP 2013-3549 A

  However, the internal waveguide 16 is easily peeled off from the substrate 1 due to the influence of heat at the time of mounting and the stress due to the usage environment, so that the yield rate of the module is lowered.

  The present invention was made to solve the above-mentioned problems, and by taking measures against the influence of heat during mounting and stress due to the use environment, it is difficult to peel off the resin structure from the substrate, and the yield rate is improved. It is an object of the present invention to provide a substrate structure and an optical module substrate that can be made to operate.

  In order to solve the above-described problems, the present invention provides a substrate structure including a substrate and a resin structure provided on the substrate, and stress relaxation that relieves stress applied to the resin structure on the substrate. A substrate structure in which a structure is formed.

  According to the present invention, a stress relaxation structure for relaxing stress is formed on a substrate. Thereby, the stress applied to the resin structure is relaxed (decreased) due to the influence of heat at the time of mounting and the use environment, and the resin structure becomes difficult to peel off from the substrate, so that the yield rate is improved.

  The resin structure may be a waveguide.

  According to this configuration, the stress applied to the waveguide of the optical module is relaxed (decreased), the waveguide is less likely to be peeled off from the substrate, and the yield rate is improved.

  The stress relaxation structure may be formed on at least one side of the waveguide.

  According to this configuration, since the stress relaxation structure is formed on at least one side of the waveguide, the stress of the waveguide can be easily relaxed.

  The stress relaxation structure may be a concave portion or a convex portion.

  According to this configuration, since the stress relaxation structure is a concave portion or a convex portion, the stress of the waveguide is easily relaxed.

  The stress relaxation structure may be formed on the surface of the substrate.

  According to this configuration, since the stress relaxation structure is formed on the surface of the substrate, the stress relaxation structure can be formed simultaneously with the waveguide, so that the process of forming the stress relaxation structure can be simplified.

  The stress relaxation structure may be formed on the back surface of the substrate.

  According to this configuration, since the stress relaxation structure is formed on the back surface of the substrate, it is not necessary to avoid wiring patterns on the surface of the substrate, so that the space in the width direction of the substrate for forming the stress relaxation structure is reduced. To do. Thereby, a board | substrate can be reduced in size and it becomes low-cost.

  The stress relaxation structure may be formed on both the front surface and the back surface of the substrate.

  According to this configuration, by forming the stress relaxation structure on both the front surface and the back surface of the substrate, the stress is further relaxed, the waveguide is more difficult to peel from the substrate, and the yield rate is further improved. .

  The waveguide may be formed in a waveguide forming groove on the surface of the substrate, and the stress relaxation structure may have the same shape as the waveguide forming groove.

  According to this configuration, since the stress relaxation structure has the same shape as the waveguide forming groove, that is, the shape of a dummy groove, the dummy groove can be formed in the same process as the waveguide forming groove, so that the stress relaxation structure is formed. The process can be simplified.

  The substrate may be a single semiconductor substrate, and the stress relaxation structure may be configured along a crystal orientation plane of the single semiconductor substrate.

  According to this configuration, since the stress relaxation structure is along the crystal orientation plane of the single semiconductor substrate, the stress relaxation structure can be easily formed.

  The single semiconductor substrate may be a silicon substrate.

  According to this configuration, since the stress relaxation structure is along the crystal orientation plane of the silicon substrate, the stress relaxation structure can be easily formed.

  The stress relaxation structure may be formed by wet etching.

  According to this configuration, the stress relaxation structure can be easily formed by wet etching.

  According to the present invention, by taking measures against the influence of heat at the time of mounting and the stress due to the use environment, it is difficult to peel the resin structure from the substrate, and the yield rate can be improved.

1 is a schematic side view of an optical module according to the present invention. It is the board | substrate which formed the stress relaxation structure of 1st Embodiment, (a) is a top view, (b) is the II sectional view taken on the line of (a). It is the board | substrate which formed the stress relaxation structure of 2nd Embodiment, (a) is a top view, (b) is the II sectional view taken on the line of (a). It is the board | substrate which formed the stress relaxation structure of 3rd Embodiment, (a) is a top view, (b) is the II sectional view taken on the line of (a). It is a board | substrate of the modification 1, (a) is a top view, (b) is the II sectional view taken on the line of (a). It is a board | substrate of the modification 2, (a) is a top view, (b) is the II sectional view taken on the line of (a). It is an internal waveguide near a mirror part, (a) is a top view, (b) is sectional drawing of (a). It is another example of the internal waveguide near a mirror part, (a) is a top view, (b) is sectional drawing of (a). It is an internal waveguide of the optical module of background art, (a) is side surface sectional drawing, (b) is side surface sectional drawing which made the front end of a core part retreat.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. Note that portions having the same configuration and operation as those of the background art are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 1 is a schematic side view of an optical module according to the present invention. In FIG. 1, an optical module includes a first substrate (mount substrate) 1 on a light emitting side, a first substrate (mount substrate) 3 on a light receiving side, and an optical fiber 2 that optically couples the first substrates 1 and 3. And.

  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. 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) 12 can be mounted with high accuracy and the position in use. It is necessary to suppress fluctuations as much as possible. For this reason, as the first substrates 1 and 3, single semiconductor substrates are employed in the present embodiment. With a single semiconductor substrate, particularly a silicon substrate, it is possible to process a highly accurate etching groove on the surface using the crystal orientation of silicon. A waveguide 16 (described later) is formed. ]. In addition, the silicon substrate has good flatness.

  If the first substrate 1 and 3 are single semiconductor substrates, the stress relaxation structure 26 described later can be configured along the crystal orientation plane of the single semiconductor substrate. Thus, since the stress relaxation structure 26 is along the crystal orientation plane of the single semiconductor substrate, the stress relaxation structure 26 can be easily formed.

  If the single semiconductor substrate is a recon substrate, the stress relaxation structure 26 is along the crystal orientation plane of the silicon substrate, so that the stress relaxation structure can be easily formed. Furthermore, the stress relaxation structure 26 can be easily formed by wet etching.

  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 for converting an electrical signal into an optical signal is flip-chip mounted with bumps 12c (see FIG. 9B) 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 wiring pattern (a patterning circuit using copper or gold sputtering) 10 formed on the surface of the first substrate 1 (see FIG. 2A).

  On the surface of the first substrate 1, a substantially V-shaped first groove (waveguide forming groove) 1a as shown in FIG. 2B and a substantially V-shaped second groove 1b deeper than the first groove 1a. Are formed continuously in the front-rear direction.

  On the front end surface of the first groove 1a, an optical path changing mirror portion 15 for bending the optical path by 90 degrees is formed at a position directly below the light emitting element 12a.

  An internal waveguide (resin structure) 16 that is optically coupled to the light emitting element 12 a of the first substrate 1 is provided in the first groove 1 a of the first substrate 1.

  Referring to FIG. 2, the internal waveguide 16 includes a core part 17 having a high refractive index through which light propagates and a clad part 18 having a refractive index lower than that. Both left and right sides of the core portion 17 are covered with a clad portion 18. The upper portion of the core portion 17 is substantially the same height as the surface of the first substrate 1, and the upper portion of the cladding portion 18 is slightly raised from the surface of the first substrate 1. The upper portion of the clad portion 18 is in close contact with the surface of the substrate 1 on both sides of the first groove 1a.

  Returning to FIG. 1, a light emitting element 12 a is mounted at a predetermined position on the surface of the first substrate 1 on which the internal waveguide 16 is provided. Between the light emitting element 12 a and the surface of the first substrate 1, Underfill is filled.

  On the other hand, the basic configuration 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, a light receiving element 12b for converting an optical signal into an electrical signal is flip-chip mounted on the surface (upper surface) of the first substrate 3 on the light receiving side 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 4a and 4b are respectively shielded by a shield case 8 attached to the surface of the second substrate 6, and the optical fiber 2 is shielded by the shield case 8 This through-hole 8a is made to penetrate.

  The optical fiber 2 is a fiber core part that can optically couple the core part 17 of the internal waveguide 16 of the first substrate 1 on the light emitting side and the core part 17 of the internal waveguide 16 of the first substrate 3 on the light receiving side. 21 inside. And it is a cord type comprised by the fiber clad 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 clad part 22. FIG. The fiber core part 21, the fiber clad part 22, and the covering part 23 are circular.

  The optical fiber 2 passes through 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 cladding portion 22 is exposed.

  And the fiber clad part 22 of the optical fiber 2 is installed in the 2nd groove | channel 1b of the 1st board | substrate 1, and the fiber clad part 22 is positioned in the rising inclination part of the boundary part with the 1st groove | channel 1a. At this time, optical coupling is performed in a positioning state in which the optical axes of the core portion 17 of the internal waveguide 16 of the first substrate 1 and the fiber core portion 21 of the optical fiber 2 coincide.

  At the position of the surface of the first substrate 1, a presser block 24 is disposed above the fiber cladding portion 22 of the optical fiber 2, and the space between the presser block 24 and the second groove 1 b is filled with an adhesive. Has been.

  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 presser block 24 while being pressed against the second groove 1b by the presser block 24. become.

  2A and 2B show the substrate 1 on which the stress relaxation structure 26 according to the first embodiment is formed. FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along the line II of FIG.

  The cross-sectional shape of the first groove 1a of the substrate 1 is substantially V-shaped. The front end 17a of the core portion 17 is set at the position of the mirror portion 15 as shown in FIG. Further, although the front end 18a of the clad portion 18 is set at a position extending to the surface of the substrate 1 more than the upper end 15c of the mirror portion 15, it is not always necessary to be at this position. These are the same even when the cross-sectional shape of the first groove 1a is substantially trapezoidal.

  On the surface of the substrate 1, a stress relaxation structure 26 is formed to relieve stress due to the influence of heat at the time of mounting and the use environment.

  The stress relaxation structure 26 is a recess formed on both sides along the first groove 1a, and specifically has the same shape as the first groove 1a. Further, as shown in FIG. 2, when the second groove 1b is formed, the second groove 1b has the same shape.

  Such a stress relaxation structure 26 has the same shape as the first groove 1a and the second groove 1b, that is, the shape of a dummy groove.

  The stress relaxation structure 26 does not necessarily have to be concave portions formed on both sides of the internal waveguide 16 along the first groove 1a and the second groove 1b. That is, it does not have to be along the first groove 1a or the second groove 1b of the internal waveguide 16. Further, it may be formed on at least one side of the first groove 1 a and the second groove 1 b of the internal waveguide 16 instead of on both sides of the first groove 1 a and the second groove 1 b of the internal waveguide 16.

  The internal waveguide 16 does not necessarily have to be formed inside the first groove 1a. That is, as shown in FIGS. 5A and 5B, the core portion 17 and the clad portion 18 may be formed on the surface (upper surface) of the substrate 1.

  The stress relaxation structure 26 does not necessarily have to be a recess. That is, as shown in FIGS. 6A and 6B, it may be a protrusion protruding from the surface of the substrate 1.

  In short, any shape may be used as long as the structure is formed on the substrate 1 and can relieve stress when the internal waveguide 16 is formed in the first groove 1a.

  If it is the structure of 1st Embodiment, the stress relaxation structure 26 which relieve | moderates the stress by the influence of the heat | fever at the time of mounting, or a use environment will be formed in the board | substrate 1. FIG. This alleviates (reduces) the stress due to the effect of heat at the time of mounting and the use environment, makes it difficult for the internal waveguide 16 to peel from the substrate 1, and improves the yield rate.

  If the stress relaxation structures 26 are formed on both sides along the first groove 1a and the second groove 1b, the stress is relaxed in the entire first groove 1a and second groove 1b of the internal waveguide 16. .

  Further, since the stress relaxation structure 26 is formed on the surface of the substrate 1, it can be formed simultaneously with the first groove 1a and the second groove 1b of the internal waveguide 16, so that the process of forming the stress relaxation structure 26 can be simplified. Become.

  Furthermore, since the stress relaxation structure 26 has the same shape as the first groove 1a and the second groove 1b, that is, the shape of a dummy groove, the dummy groove can be formed in the same process as the first groove 1a and the second groove 1b. The formation process of the stress relaxation structure 26 can be simplified.

  3A and 3B show the substrate 1 on which the stress relaxation structure 26 according to the second embodiment is formed. FIG. 3A is a plan view and FIG. 3B is a cross-sectional view taken along the line II of FIG. The difference from the first embodiment is that the stress relaxation structure 26 is formed not on the front surface of the substrate 1 but on the back surface.

  If it is the structure of 2nd Embodiment, in addition to the effect similar to 1st Embodiment, the pattern 10 for wiring etc. on the surface of the board | substrate 1 etc. are avoided by forming the stress relaxation structure 26 in the back surface of the board | substrate 1. Since this is not necessary, the space in the width direction of the substrate 1 for forming the stress relaxation structure 26 is reduced. Thereby, the board | substrate 1 can be reduced in size and it becomes low-cost.

  4A and 4B show the substrate 1 on which the stress relaxation structure 26 according to the third embodiment is formed. FIG. 4A is a plan view and FIG. 4B is a cross-sectional view taken along the line II of FIG. The difference from the first embodiment is that the stress relaxation structure 26 is formed on both the front surface and the back surface of the substrate 1.

  With the configuration of the third embodiment, by forming the stress relaxation structure 26 on both the front surface and the back surface of the substrate 1, the stress is further relaxed, and the core portion 17 is more difficult to peel from the substrate 1, resulting in a yield. The rate will be improved.

  In each of the embodiments, as shown in FIG. 7, the front end 17 a of the core portion 17 is set at the position of the mirror portion 15, and the front end 18 a of the cladding portion 18 is closer to the surface of the substrate 1 than the upper end 15 c of the mirror portion 15. It is set at the extended position.

  On the other hand, as shown in FIG. 8, the front end 17a of the core portion 17 is set at a position retracted from the mirror portion 15, and the front end 18a of the clad portion 18 is a substantially V-shaped groove portion of the first groove 1a. Can be set to the position of the front end 1d.

  According to this configuration, the front end 17a of the core portion 17 is retracted from the mirror portion 15, so that the temperature rise of the core portion 17 is suppressed. Therefore, the core portion 17 is difficult to peel off from the substrate 1, and the yield rate is increased. To improve. The front end 17 a of the core portion 17 is retracted from the mirror portion 15, and the front end 18 a of the cladding portion 18 is retracted from the front end 17 a of the core portion 17. From this, the adhesion force of the core portion 17 to the substrate 1 is reduced, but since the stress relaxation structure 26 is formed on the substrate 1, the core portion 17 is difficult to peel from the substrate 1 at this point. The yield rate is improved.

  Although each said embodiment was the board | substrate 1 for optical modules, it is not restricted only to the board | substrate 1 for optical modules. That is, it goes without saying that the present invention can be applied to a substrate for other purposes as long as it is a substrate structure that forms a resin structure on the substrate.

1 First substrate (substrate)
1a 1st groove (groove for waveguide formation)
1b Second groove 12a Light emitting element 12b Light receiving element 15 Mirror part 16 Internal waveguide (resin structure)
17 Core part 17a Front end 18 Clad part 26 Stress relaxation structure

Claims (11)

In a substrate comprising a substrate and a resin structure provided on the substrate,
A substrate structure having a stress relaxation structure for relaxing stress applied to the resin structure on the substrate.   The optical module substrate, wherein the resin structure is a waveguide.   The optical module substrate according to claim 2, wherein the stress relaxation structure is formed on at least one side of the waveguide.   The said stress relaxation structure is a recessed part or a convex part, The board | substrate for optical modules as described in any one of Claims 1-3 characterized by the above-mentioned.   The optical module substrate according to any one of claims 1 to 4, wherein the stress relaxation structure is formed on a surface of the substrate.   The optical module substrate according to claim 1, wherein the stress relaxation structure is formed on a back surface of the substrate.   The optical module substrate according to claim 1, wherein the stress relaxation structure is formed on both a front surface and a back surface of the substrate.   8. The waveguide according to claim 2, wherein the waveguide is formed in a waveguide forming groove on the surface of the substrate, and the stress relaxation structure has the same shape as the waveguide forming groove. The substrate for optical modules as described in any one of Claims.   The optical module substrate according to claim 1, wherein the substrate is a single semiconductor substrate, and the stress relaxation structure is along a crystal orientation plane of the single semiconductor substrate.   The optical module substrate according to claim 9, wherein the single semiconductor substrate is a silicon substrate.   The optical module substrate according to claim 10, wherein the stress relaxation structure is formed by wet etching.

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