JP2015222312A - Optical transmission module and packaging structure of optical block - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission module with which it is possible to align the optical axes of an optical element and an optical block without using a protrusion and a fitting hole for positioning and suppress the effect of heat from a heat generating substance, and the packaging structure of the optical block.SOLUTION: An optical transmission module 1 comprises: a multilayer circuit board 2 in which a plurality of wiring layers are formed and which has first and second principal planes 2a, 2b; an optical element 3 mounted on the bottom face 21a of a recess 21 and electrically connected to a second wiring layer 20from an uppermost layer; a circuit element 4 electrically connected to a second wiring layer 20from a lowermost layer; an optical block 5 disposed position-adjustably in parallel to the first principal plane 2a and optically coupled with the optical element 3; and an adhesive 6 for bonding the first principal plane 2a and the optical block 5.

Description

  The present invention relates to an optical transmission module and an optical block mounting structure.

  In recent years, with the miniaturization of an optical transmission module, an optical block in which a lens and an optical fiber are integrated is used. Conventionally, in order to suppress optical transmission loss as much as possible, an optical transmission module in which a lens or an optical block is fixed to a substrate or the like with an adhesive after optical axis alignment between a laser diode and a lens has been proposed (for example, (See Patent Documents 1 and 2).

  The optical transmission module described in Patent Document 1 includes a Si substrate having a trapezoidal groove, a spherical lens arranged in the groove of the Si substrate, a wall member around the lens, a wall member and a lens, And an adhesive layer for bonding the wall member and the Si substrate, and a laser diode mounted on the Si substrate. According to this configuration, compared with the case where the lens is directly bonded to the Si substrate with an adhesive without using the wall member, even if the Si substrate receives heat and the temperature rises, the wall member does not peel from the Si substrate, Further, no cracks are generated in the Si substrate, and it is said that durability is improved.

  An optical transmission module described in Patent Document 2 includes a circuit board on which an optical element is mounted, a lens block cradle bonded to the circuit board with an adhesive and having a fitting hole, and a lens block having a lens and a protrusion. (Optical block), and the lens block is positioned with respect to the lens block pedestal by fitting the projection of the lens block into the fitting hole of the lens block pedestal.

JP 2005-17359 A JP 2011-150073 A

  However, since the optical transmission module described in Patent Document 1 has a lens bonded to the same surface as the surface of the Si substrate on which the laser diode is mounted, a heating element such as a driver IC is mounted on the lower surface of the Si substrate. In the case of adopting such a configuration, the temperature of the adhesive rises due to heat from the heating element, which may cause problems such as deformation of the Si substrate and peeling of the wall member.

  In addition, since the optical transmission module described in Patent Document 2 performs positioning using the projection of the lens block and the fitting hole of the lens block cradle, the optical axis alignment can be made unnecessary. High precision molding is required for the joint hole.

  Accordingly, an object of the present invention is to provide light that can align the optical axis of the optical element and the optical block without using positioning protrusions and fitting holes, and can suppress the influence of heat from the heating element. A transmission module and an optical block mounting structure are provided.

  In order to solve the above problems, the present invention provides a multilayer substrate having a plurality of wiring layers formed therein and having first and second principal surfaces, and the first principal surface of the multilayer substrate. An optical element mounted on a lower first surface and electrically connected to the wiring layer on the second main surface side than the uppermost layer of the plurality of wiring layers; and the second element of the multilayer substrate. A circuit element mounted on a surface on the main surface side and electrically connected to the optical element, and arranged on the first main surface side of the multilayer substrate so as to be position-adjustable in parallel with the first main surface An optical transmission module comprising: an optical block that is optically coupled to the optical element; and an adhesive that bonds the second block higher than the first surface of the multilayer substrate to the optical block. provide.

  The first surface may be a bottom surface of a recess formed in the first main surface. The second surface may be a surface that is higher than the bottom surface of the recess and lower than the first main surface.

  The surface on the second main surface side on which the circuit element is mounted is a surface closer to the first main surface side than the second main surface, and the circuit element is electrically connected to the optical element. It may be connected to.

  The optical element may be a light emitting element or a light receiving element, and the circuit element may be a driving element for driving the light emitting element or an amplifying element for amplifying an output signal of the light receiving element.

  In order to solve the above problems, the present invention provides a multilayer substrate having a plurality of wiring layers formed therein and having first and second main surfaces, which is lower than the first main surface. An optical element is mounted on one surface, and the optical element is electrically connected to the wiring layer closer to the second main surface than the uppermost layer of the plurality of wiring layers. In the mounting structure of the optical block that is arranged on the main surface side so as to be position-adjustable in parallel with the first main surface and optically couples with the optical element, the first structure is higher than the first surface of the multilayer substrate. An optical block mounting structure is provided in which two surfaces and the optical block are bonded together with an adhesive.

  According to the present invention, it is possible to perform optical axis alignment between the optical element and the optical block without using positioning protrusions and fitting holes, and it is possible to suppress the influence of heat from the heating element.

FIG. 1 is a cross-sectional view showing a schematic configuration example of an optical transmission module according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a schematic configuration example of an optical transmission module according to the second embodiment of the present invention. FIG. 3 is a cross-sectional view showing a schematic configuration example of an optical transmission module according to the third embodiment of the present invention. FIG. 4 is a sectional view showing a schematic configuration example of an optical transmission module according to the fourth embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, about the component which has the substantially same function, the same code | symbol is attached | subjected and the duplicate description is abbreviate | omitted.

[First Embodiment]
FIG. 1 is a cross-sectional view showing a schematic configuration example of an optical transmission module according to the first embodiment of the present invention.

(Overall configuration of optical transmission module)
The optical transmission module 1 has a plurality (five in the present embodiment) of wiring layers 20 _{1 to} 20 ₅ (referred to collectively as “wiring layers 20”) formed therein. A multilayer substrate 2 having a second principal surface 2a, 2b; an optical element 3 mounted on a bottom surface 21a of a recess 21 formed in the first principal surface 2a of the multilayer substrate 2; The circuit element 4 mounted on the bottom surface 22a of the recess 22 formed in the main surface 2b and electrically connected to the optical element 3, the optical block 5 optically coupled to the optical element 3, and the first of the multilayer substrate 2 1 is provided with an adhesive 6 for adhering the main surface 2a and the optical block 5 to each other. Here, the bottom surface 21a is an example of a first surface lower than the first main surface 2a. The first main surface 2a bonded to the optical block 5 is an example of a second surface that is higher than the bottom surface (first surface) 21a. The bottom surface 22a of the recess 22 on which the circuit element 4 is mounted is an example of a surface closer to the first main surface 2a side than the second main surface 2b.

  The optical transmission module 1 is accommodated in the case 10 in a state where the optical element 3, the circuit element 4, and the optical block 5 are mounted on the multilayer substrate 2. The case 10 has a substantially box shape including a bottom wall 10a, side walls 10b and 10c, and an upper wall 10d. The case 10 is made of a metal such as aluminum in order to suppress electromagnetic noise radiated to the outside. The multilayer substrate 2 is supported by a support base 11 made of metal, resin, or the like disposed between the second main surface 2b and the bottom wall 10a of the case 10. Further, the circuit element 4 is in contact with the bottom wall 10a of the case 10 through a heat dissipation sheet 12 made of a resin film for heat dissipation of the circuit element 4.

(Configuration of multilayer board)
The multilayer substrate 2 is configured by alternately laminating wiring layers 20 _{1 to} 20 ₅ and insulating layers 23 made of glass epoxy resin or the like. The wiring layers 20 _{1 to} 20 ₅ can be formed from a good conductor such as copper, silver, or gold, for example. Each wiring layer 20 is connected by a via hole 24 at an appropriate position. The recess 21 formed in the first main surface 2a of the multilayer substrate 2 is formed of, for example, four side surfaces and a bottom surface 21a. The recess 22 formed in the second main surface 2b of the multilayer substrate 2 is formed of, for example, four side surfaces and a bottom surface 22a.

(Configuration of optical element)
The optical element 3 is a light emitting element that transmits an optical signal or a light receiving element that receives an optical signal. Examples of the former include semiconductor laser elements such as VCSELs (surface emitting lasers) and light emitting elements such as LEDs (light emitting diodes). Further, as the latter example, a light receiving element such as a photodiode can be cited. Optical device 3 is electrically connected by a bonding wire 31 through the second wiring layer 20 ₄ to the electrode 25 from the uppermost layer. Instead of the bonding wire 31, a wiring pattern is formed on the wiring layer 20 _4, the optical element 3 is mounted on the wiring layer 20 ₄ by flip-chip mounting, it is also possible to perform the electrical connection.

(Configuration of circuit elements)
The circuit element 4 is a driver IC that drives the light emitting element if the optical element 3 is a light emitting element, and is a preamplifier IC that amplifies the output signal of the light receiving element if the optical element 3 is a light receiving element. The circuit element 4 is flip-chip mounted on the electrode 26 formed on the _second wiring layer 202 from the bottom layer via the solder 7. The circuit element 4 is not limited to flip chip mounting, and may be wire bonding mounting. Place the circuit element 4 directly below the bottom surface 21a of the first recess 21 formed in the main surface 2a, electrically connecting the optical element 3 to the wiring layer 20 ₄ of the second layer from the uppermost layer, circuit elements 4 Is electrically connected to the _second wiring layer 202 from the lowest layer, the length of the signal transmission path between the optical element 3 and the circuit element 4 can be shortened, and the optical element 3 and the circuit element 4 can be shortened. It is possible to suppress degradation of signals transmitted between the two.

The circuit element 4 may be electrically connected to the wiring layer 20 ₁ of the bottom layer. The optical element 3 even when in comparison with the case that is electrically connected to the wiring layer 20 ₅ of the uppermost layer, it is possible to shorten the length of the signal transmission path between the optical element 3 and the circuit element 4.

(Configuration of optical block)
The optical block 5 includes a block main body 50 having a lens portion 50a, a mirror 51 incorporated in the block main body 50, and an optical fiber 52 arranged so as to be orthogonal to the optical axis 3a of the optical element 3. By setting it as such a structure, the optical block 5 can be reduced in size.

  The block main body 50 has, for example, a rectangular outer shape, and includes, as an example, a quadrangular columnar base 50b and a square cylindrical leg 50c. A fitting recess 50d into which the optical fiber 52 is fitted is formed in the base 50b. The optical block 5 is assembled by fitting the tip of the optical fiber 52 into the fitting recess 50d. The convex lens portion 50a is formed on the surface of the base portion 50b facing the optical element 3. In order to enable optical axis alignment between the optical element 3 and the lens portion 50 a of the optical block 5, the width of the leg portion 50 c is set to be sufficiently smaller than the width of the concave portion 21. The leg part 50c has an appropriate length in order to provide a predetermined distance between the optical element 3 and the lens part 50a. The block main body 50 is formed of a material transparent to the optical signal output from the optical element 3 or the optical signal received by the optical element 3, for example, an acrylic resin. The block body 50 may have a cylindrical outer shape.

  The optical fiber 52 includes a core and a clad formed around the core. The optical fiber 52 may have a coating layer around the cladding. In this case, the fitting recess 50d may be fitted with the covering layer, or the leading end side covering layer may be peeled off and fitted into the fitting recess 50d.

  For example, an ultraviolet curable resin can be used as the adhesive 6. The adhesive 6 is not limited to the ultraviolet curable resin, and other adhesives may be used.

(Assembling the optical transmission module)
The optical transmission module 1 is assembled as follows, for example. The optical element 3 is mounted on the bottom surface 21 a of the recess 21 formed on the first main surface 2 a of the multilayer substrate 2. At this time, the optical element 3 and the electrode 25 are connected by the bonding wire 31 as needed. The circuit element 4 is mounted on the bottom surface 22a of the recess 22 formed on the second main surface 2b of the multilayer substrate 2. At this time, the circuit element 4 is electrically connected to the electrode 26 by the solder 7.

  The optical block 5 is placed on the multilayer substrate 2 with the tip surface 50e of the leg portion 50c of the optical block 5 in contact with the bottom surface 21a of the recess 21. Next, the adhesive 6 is applied between the outer peripheral surface 50f of the optical block 5 and the first main surface 2a. When applying the adhesive 6, an air layer is formed in the space ε formed by the recess 21, the adhesive 6, and the optical block 5 (see FIG. 1). By forming the air layer, the heat insulation effect is increased, and a decrease in the adhesive strength of the adhesive 6 can be suppressed. On the other hand, the space ε may be filled with the adhesive 6. By filling the space ε with the adhesive 6, the adhesive strength can be increased.

  Next, when the optical element 3 is a light emitting element, the circuit element 4 is driven to output an optical signal from the optical element 3. The optical signal output from the optical element 3 is collected by the lens unit 50 a, then reflected by the mirror 51 and incident on the optical fiber 52. Optical axis alignment is performed by moving the optical block 5 in the direction along the first main surface 2a so that the optical intensity of the optical signal is maximized while observing the optical intensity of the optical signal output from one end face of the optical fiber 52. Do. The adhesive 6 is cured by irradiating the adhesive 6 with ultraviolet rays at the position of the optical block 5 where the light intensity of the optical signal is maximized (in a state where the optical axis is aligned).

  On the other hand, when the optical element 3 is a light receiving element, an optical signal emitted from the optical fiber 52 is reflected by the mirror 51, collected by the lens unit 50 a, and incident on the optical element 3. The circuit element 4 outputs a signal having a voltage corresponding to the light intensity of the optical signal received by the optical element 3. While observing the voltage of the output signal of the circuit element 4, the adhesive 6 is cured by irradiating the adhesive 6 with ultraviolet rays at the position of the optical block 5 where the voltage of the output signal is maximum.

  After the optical axis alignment of the optical block 5 is performed as described above, the heat radiating sheet 12 is attached to the circuit element 4, and the second main surface 2 b of the multilayer substrate 2 is attached to the bottom wall 10 a of the case 10 via the support base 11. Place on top.

(Operation of optical transmission module)
Next, an example of the operation of the optical transmission module 1 will be described. When the optical element 3 is a light emitting element, the optical transmission module 1 operates as follows. That is, the circuit element 4 is driven to output an optical signal from the optical element 3. The optical signal output from the optical element 3 is collected by the lens unit 50a, then reflected by the mirror 51 and incident on one end face of the optical fiber 52, and the other end face (not shown) of the optical fiber 52. Exits from.

  On the other hand, when the optical element 3 is a light receiving element, the optical transmission module 1 operates as follows. That is, an optical signal incident on the other end face (not shown) of the optical fiber 52 and emitted from the one end face of the optical fiber 52 is reflected by the mirror 51, collected by the lens unit 50 a, and condensed on the optical element 3. Incident. The optical element 3 outputs a signal having a voltage corresponding to the light intensity of the received optical signal. The circuit element 4 amplifies the signal output from the optical element 3 and outputs the amplified signal to a processing circuit or the like.

(Operation and effect of the first embodiment)
According to the present embodiment, the following operations and effects are achieved.
(1) Since the inner diameter of the recess 21 formed on the first main surface 2a of the multilayer substrate 2 is larger than the outer diameter of the leg portion 50c of the optical block 5, the optical block 5 is parallel to the first main surface 2a. The optical axis of the optical element 3 and the optical block 5 can be adjusted by adjusting the position.
(2) Since the optical block 5 and the multilayer substrate 2 are bonded to each other at the first main surface 2a higher than the bottom surface 21a of the recess 21 on which the optical element 3 is mounted, the optical block 5 and the multilayer substrate 2 are generated from the circuit element 4 as a heating element. Heat is not easily transmitted to the adhesive 6, a decrease in the adhesive strength of the adhesive 6 is suppressed, and the optical block 5 is difficult to peel off from the multilayer substrate 2. That is, the optical axis alignment of the optical element 3 and the optical block 5 can be performed without using the positioning projection and the fitting hole, and the influence of the heat of the circuit element 4 as the heating element can be suppressed.
(3) an optical element 3 is electrically connected from the top layer to the second wiring layer 20 _4, since the circuit element 4 connecting from the bottom layer in the second wiring layer 20 _2, the optical element 3 top electrically connected to the upper wiring layer 20 _5, as compared with the case of connecting the circuit elements 4 on the wiring layer 20 ₁ of the bottom layer, to reduce the length of the signal transmission path between the optical element 3 and the circuit elements 4 It is possible to suppress deterioration of signals transmitted between the optical element 3 and the circuit element 4.

[Second Embodiment]
FIG. 2 is a cross-sectional view showing a schematic configuration example of an optical transmission module according to the second embodiment of the present invention. In the first embodiment, the outer peripheral surface 50f of the leg portion 50c of the block body 50 of the optical block 5 is bonded to the first main surface 2a of the multilayer substrate 2 with the adhesive 6. However, in the present embodiment, the block The shape of the main body 50 is changed.

  The block main body 50 according to the present embodiment is provided with a flange portion 50g on the side surface of the leg portion 50c, and the side surface and the upper surface of the flange portion 50g are bonded to the first main surface 2a of the multilayer substrate 2 with the adhesive 6. . Even in such a configuration, the same operations and effects as the above-described (1) to (3) of the first embodiment are exhibited. Further, according to the second embodiment, it is possible to increase the area of the block body 50 that contacts the adhesive 6 as compared with the first embodiment.

[Third Embodiment]
FIG. 3 is a cross-sectional view showing a schematic configuration example of an optical transmission module according to the third embodiment of the present invention. In the first embodiment, the outer peripheral surface 50f of the leg portion 50c of the block main body 50 of the optical block 5 is bonded to the first main surface 2a of the multilayer substrate 2 with the adhesive 6. However, in the present embodiment, the concave portion The shape of 21 is changed.

  In the multilayer substrate 2 of the present embodiment, a step portion is provided in the concave portion 21, and the outer peripheral surface 50 f of the leg portion 50 c of the block body 50 is bonded to the step surfaces 21 b and 21 c of the concave portion 21 with the adhesive 6. Here, the step surface 21b bonded to the optical block 5 is an example of a second surface.

  Even in such a configuration, the same operations and effects as the above-described (1) to (3) of the first embodiment are exhibited. Further, according to the third embodiment, it is possible to increase the area of the multilayer substrate 2 that contacts the adhesive 6 as compared with the first embodiment.

[Fourth Embodiment]
FIG. 4 is a sectional view showing a schematic configuration example of an optical transmission module according to the fourth embodiment of the present invention. In the first embodiment, the tip of the leg portion 50c of the block main body 50 of the optical block 5 is brought into contact with the bottom surface 21a of the recess 21. However, in the present embodiment, the shape of the leg portion 50c is changed. is there.

  The block main body 50 according to the present embodiment includes a base portion 50b similar to that of the first embodiment and leg portions 50c having a length shorter than that of the first embodiment. In the block main body 50 of the present embodiment, the front end surface 50e of the leg portion 50c is brought into contact with the first main surface 2a of the multilayer substrate 2, and the outer peripheral surface 50f of the leg portion 50c is bonded to the first main surface by the adhesive 6. Adhered to 2a. Even in such a configuration, the same operations and effects as the above-described (1) to (3) of the first embodiment are exhibited. Further, according to the fourth embodiment, the amount of the adhesive 6 can be reduced as compared with the first embodiment, and the curing time of the adhesive 6 can be shortened.

  If the predetermined distance can be set between the optical element 3 and the lens unit 50a, the block main body 50 may be configured by only the base 50b without providing the block main body 50 with the legs 50c.

[Other embodiments]
The embodiments of the present invention are not limited to the above-described embodiments, and various embodiments are possible. For example, although one optical element 3 has been described in the above embodiment, the optical element 3 may be a light emitting element array or a light receiving element array. In this case, a plurality of lens portions 50a are formed in an array on the block body 50. Further, a ribbon fiber composed of a plurality of optical fibers 52 may be used. The optical element 3 may be a combination of a light emitting element and a light receiving element.

  In the above embodiment, the optical element 3 is mounted on the bottom surface 21a of the recess 21. However, on the bottom surface of the step portion formed by the three side surfaces and the bottom surface at the end of the first main surface 2a of the multilayer substrate 2. The optical element 3 may be mounted. Further, the optical element 3 may be mounted on the bottom surface of the step portion formed by the two side surfaces and the bottom surface at the corner portion of the first main surface 2a of the multilayer substrate 2. Further, the optical element 3 may be mounted on the bottom surface of the stepped portion formed by the curved side surface and the bottom surface at the end or corner of the first main surface 2a of the multilayer substrate 2.

  In the above embodiment, the circuit element 4 is mounted on the bottom surface 22 a of the recess 22, but on the bottom surface of the step portion formed by the three side surfaces and the bottom surface at the end of the second main surface 2 b of the multilayer substrate 2. The circuit element 4 may be mounted. In addition, the circuit element 4 may be mounted on the bottom surface of the step portion formed by the two side surfaces and the bottom surface at the corner of the second main surface 2b of the multilayer substrate 2. In addition, the circuit element 4 may be mounted on the bottom surface of the stepped portion formed by the curved side surface and the bottom surface at the end or corner of the second main surface 2b of the multilayer substrate 2. By mounting the circuit element 4 on the bottom surface of the step portion at the end or corner, it is easier to radiate heat in the side surface direction than when the circuit element 4 is mounted on the bottom surface 22 a of the recess 22.

DESCRIPTION OF SYMBOLS 1 ... Optical transmission module, 2 ... Multilayer substrate, 2a ... 1st main surface, 2b ... 2nd main surface,
3 ... Optical element, 3a ... Optical axis, 4 ... Circuit element, 5 ... Optical block, 6 ... Adhesive, 7 ... Solder,
10 ... case, 10a ... bottom wall, 10b, 10c ... side wall, 10d ... upper wall,
DESCRIPTION OF SYMBOLS 11 ... Support stand, 12 ... Radiation sheet, 20, 201-205 ... Wiring layer, 21 ... Recessed part,
21a ... bottom surface, 21b, 21c ... step surface, 22 ... concave, 22a ... bottom surface, 23 ... insulating layer,
24 ... via hole, 25, 26 ... electrode, 31 ... bonding wire,
50 ... Block body, 50a ... Lens part, 50b ... Base part, 50c ... Leg part,
50d: fitting recess, 50e: tip surface, 50f ... outer peripheral surface, 50g ... collar, 51 ... mirror,
52. Optical fiber

Claims (6)

A multilayer substrate having a plurality of wiring layers formed therein and having first and second main surfaces;
Mounted on a first surface lower than the first main surface of the multilayer substrate, and electrically connected to the wiring layer on the second main surface side of the uppermost layer of the plurality of wiring layers An optical element;
A circuit element mounted on the second principal surface side of the multilayer substrate and electrically connected to the optical element;
An optical block disposed on the first main surface side of the multilayer substrate so as to be position-adjustable in parallel with the first main surface and optically coupled to the optical element;
An adhesive that bonds the second block higher than the first surface of the multilayer substrate to the optical block;
Optical transmission module with   The optical transmission module according to claim 1, wherein the first surface is a bottom surface of a recess formed in the first main surface.   The optical transmission module according to claim 2, wherein the second surface is a surface that is higher than a bottom surface of the recess and lower than the first main surface. The surface on the second main surface side on which the circuit element is mounted is a surface closer to the first main surface side than the second main surface,
The circuit element is electrically connected to the optical element;
The optical transmission module according to claim 1. The optical element is a light emitting element or a light receiving element,
5. The optical transmission module according to claim 1, wherein the circuit element is a driving element that drives the light emitting element or an amplifying element that amplifies an output signal of the light receiving element. 6. A multilayer substrate having a plurality of wiring layers formed therein and having first and second main surfaces, wherein an optical element is mounted on a first surface lower than the first main surface, and the optical element is Parallel to the first main surface of the multilayer substrate electrically connected to the wiring layer closer to the second main surface than the uppermost layer among the plurality of wiring layers In the mounting structure of the optical block that is arranged so that the position can be adjusted and is optically coupled to the optical element,
An optical block mounting structure in which a second surface higher than the first surface of the multilayer substrate is bonded to the optical block with an adhesive.

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