JP2022013030A - Optical module mounting board, optical module, manufacturing method of optical module mounting board, and manufacturing method of optical module - Google Patents

Abstract

To provide an optical module mounting board capable of easily and accurately forming a cavity structure.SOLUTION: An optical module mounting board comprises: an insulating translucent substrate; a first wiring layer provided on a first principal surface of the translucent substrate; a second wiring layer provided on a second principal surface of the translucent substrate; and a cavity wall provided around the second wiring layer. A first opening is formed inside of the first wiring layer. A first optical element is mounted on an upper face of the first wiring layer. In the second wiring layer, a second opening is formed at a position corresponding to the first opening. The cavity wall is provided to form a cavity structure defining a surface of the second wiring layer as a first bottom face, defining the second principal surface of the translucent substrate exposed from the second opening as a second bottom face and defining the cavity wall per se as a sidewall of a predetermined height. A second optical element is mounted on an upper face of the cavity wall.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical module mounting substrate, an optical module, a method for manufacturing an optical module mounting substrate, and a method for manufacturing an optical module.

In recent years, there has been an increasing demand for high-speed, large-capacity data transmission not only in mission-critical equipment used in base stations and data centers, but also in consumer equipment such as 4K and 8K televisions and digital signage. Optical communication technology is one of the technologies to realize this. In optical communication technology, there is a demand for an optical module that can be manufactured in a compact size and at low cost. As such an optical module, one in which a light emitting element or a light receiving element is face-down mounted on a substrate is known. Further, miniaturization of the entire optical module including optical elements such as a lens is being studied.

For example, in Patent Document 1, a through hole for inserting an optical fiber is provided in a substrate, a support portion for supporting the optical fiber and a small diameter portion having a smaller diameter than the support portion are provided in the through hole, and the support portion and the small diameter portion are provided. The invention of an optical module that holds a ball lens at the boundary is disclosed. In the present invention, the size of the optical module can be reduced by accommodating the ball lens in the substrate.

Japanese Unexamined Patent Publication No. 2004-309925

However, in the structure disclosed in Patent Document 1, it is necessary to form a finer small diameter portion in the narrow through hole into which the optical fiber is inserted to provide a step. For this reason, there is a problem that it is difficult to process with high accuracy and it is difficult to obtain reproducibility.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical module mounting substrate capable of easily and accurately forming a cavity structure.

In order to solve the above problems, the optical module mounting substrate of the present invention includes an insulating translucent substrate, a first wiring layer provided on the first main surface of the translucent substrate, and a translucent substrate. It has a second wiring layer provided on the second main surface of the above, and a cavity wall provided around the second wiring layer. A first opening is formed inside the first wiring layer. A first optical element is mounted on the upper surface of the first wiring layer. A second opening is formed at a position of the second wiring layer corresponding to the first opening. The cavity wall has a cavity structure in which the surface of the second wiring layer is the first bottom surface, the second main surface of the translucent substrate exposed from the second opening is the second bottom surface, and itself is the side wall of a predetermined height. It is provided to form. A second optical element is mounted on the upper surface of the cavity wall.

Further, the method for manufacturing an optical module mounting substrate of the present invention includes the above-mentioned optical module mounting substrate and an optical component housed in a cavity structure of the optical module mounting substrate.

Further, in the method for manufacturing an optical module mounting substrate of the present invention, a first wiring layer in which a first opening is formed inside on a first main surface of a translucent substrate and a first optical element is mounted on the upper surface. To form. Then, a second wiring layer having a second opening formed at a position corresponding to the first opening on the second main surface of the translucent substrate is formed. Further, a predetermined height is formed so as to form a cavity structure in which the surface of the second wiring layer is the first bottom surface, the second main surface of the translucent substrate exposed from the second opening is the second bottom surface, and the side wall is itself. A cavity wall is formed on the upper surface on which the second optical element is mounted.

Further, in the method for manufacturing an optical module of the present invention, the optical module mounting substrate is manufactured by the above-mentioned manufacturing method for the optical module mounting substrate, and the optical components accommodated in the cavity structure are mounted.

The effect of the present invention is to be able to provide an optical module mounting substrate capable of easily and accurately forming a cavity structure.

It is sectional drawing which shows the optical module mounting substrate of 1st Embodiment. It is a top view which shows the 1st main surface of the optical module mounting substrate of 1st Embodiment. It is a top view which shows the 2nd main surface of the optical module mounting substrate of 1st Embodiment. It is sectional drawing which shows the optical module mounting substrate of 2nd Embodiment. It is a top view which shows the 1st main surface of the optical module mounting substrate of 2nd Embodiment. It is a top view which shows the 2nd main surface of the optical module mounting substrate of 2nd Embodiment. It is sectional drawing which shows the 1st part of the manufacturing method of the optical module mounting substrate of 2nd Embodiment. It is sectional drawing which shows the 1st part of the manufacturing method of the optical module mounting substrate of 2nd Embodiment. It is sectional drawing which shows the 1st part of the manufacturing method of the optical module mounting substrate of 2nd Embodiment. It is sectional drawing which shows the 1st part of the manufacturing method of the optical module mounting substrate of 2nd Embodiment. It is sectional drawing which shows the 1st part of the manufacturing method of the optical module mounting substrate of 2nd Embodiment. It is sectional drawing which shows the optical module of 3rd Embodiment. It is sectional drawing which shows the optical module of 4th Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, although the embodiments described below have technically preferable limitations for carrying out the present invention, the scope of the invention is not limited to the following. Note that similar components in each drawing may be numbered the same and description may be omitted.

(First Embodiment)
FIG. 1 is a cross-sectional view showing the optical module mounting substrate 10 of the present embodiment. The optical module mounting substrate 10 includes an insulating translucent substrate 1, a first wiring layer 2 provided on the first main surface of the translucent substrate 1, and a second main surface of the translucent substrate 1. It has a second wiring layer 3 provided in the above, and a cavity wall 4 provided around the second wiring layer 3. The translucency of the translucent substrate 1 means that it has translucency for light having a predetermined wavelength, and does not necessarily have to be transparent to visible light.

A first opening 2a is formed inside the first wiring layer 2, and the first main surface of the translucent substrate 1 is exposed in the first opening 2a. The first optical element d is mounted on the upper surface of the first wiring layer 2.

A second opening 3a is formed at a position corresponding to the first opening 2a of the second wiring layer 3, and the second main surface of the translucent substrate 1 is exposed at the second opening 3a.

The cavity wall 4 has a side wall having a predetermined height, with the surface of the second wiring layer 3 as the first bottom surface and the second main surface of the translucent substrate 1 exposed from the second opening 3a as the second bottom surface. It is provided so as to form the cavity structure 5. The second optical element e is mounted on the upper surface of the cavity wall 4.

FIG. 2 is a plan view of the optical module mounting substrate 10 when viewed from the first main surface side of the translucent substrate 1. The first wiring layer 2 is provided on the first main surface of the translucent substrate 1, and the first opening 2a is formed inside the first wiring layer 2. In the first opening 2a, the first main surface of the translucent substrate 1 is exposed.

FIG. 3 is a plan view of the optical module mounting substrate 10 when viewed from the second main surface side of the translucent substrate 1. The second wiring layer 3 is provided on the second main surface of the translucent substrate 1, and the second opening 3a is formed at a position corresponding to the first opening 2a inside the second wiring layer 3. ing. In the second opening 3a, the second main surface of the translucent substrate 1 is exposed.

In the above configuration, the first bottom surface in contact with the cavity wall 4 of the cavity structure 5 is formed by the second wiring layer 3. With such a configuration, for example, the cavity wall 4 is formed of resin and the second wiring layer 3 is formed of a metal film, so that the etching selection ratio can be increased. Therefore, the patterning of the cavity wall 4 can be easily and accurately performed. As a result, the cavity structure 5 can be easily and accurately formed. In the above description, an example of a rectangular pattern is used in which the first opening, the second opening, and the upper surface of the cavity wall have a rectangular pattern, but the pattern can be any shape that satisfies the desired optical performance.

Further, although not shown, electrodes and wiring can be arranged on the first wiring layer 2 to form a shape that satisfies desired electrical characteristics and optical characteristics.

(Second embodiment)
In this embodiment, a specific configuration example of the optical module mounting substrate of the first embodiment will be described. FIG. 4 is a cross-sectional view showing a configuration example of the optical module mounting substrate 1000 of the present embodiment.

The optical module mounting substrate 1000 is a multilayer substrate in which a wiring layer and an insulating layer are provided on both sides of the insulating translucent substrate 100. A first wiring layer 200 and a first insulating layer 210 that covers a part of the first wiring layer 200 are provided on the first main surface of the translucent substrate 100. A first opening 201 is formed inside the first wiring layer 200, and the first main surface of the translucent substrate 100 is exposed in the first opening 201. For example, an optical element 400 is mounted on the upper surface of the first wiring layer 200. The translucency of the translucent substrate 1 means that it has translucency for light having a predetermined wavelength, and does not necessarily have to be transparent to visible light.

On the second main surface of the translucent substrate 100, a second wiring layer 300, a substrate adhesive layer 310, a second insulating layer 320, and a third wiring layer 330 are provided in this order from the side closest to the translucent substrate 100. , A third insulating layer 340 is provided. A second opening 301 is formed at a position corresponding to the first opening 201 of the second wiring layer 300, and the second main surface of the translucent substrate 1 is exposed in the second opening 301.

The substrate adhesive layer 310, the second insulating layer 320, the third wiring layer 330, and the third insulating layer 340 are formed with openings having a diameter larger than that of the second opening 301. As a result, the cavity structure 350 is formed. In the example of FIG. 4, the bottom surface of the cavity structure 350 is formed by a first bottom surface made of a second wiring layer 300 and a second bottom surface made of a second main surface of the translucent substrate 100 exposed from the second opening 301. Has been done. Further, the side wall 351 of the cavity structure 350 is formed by the side surface of the opening of the substrate adhesive layer 310, the second insulating layer 320, and the third insulating layer 340. By providing the cavity structure 350, for example, an optical element such as an optical component 500 having a convex portion can be compactly mounted. In the example of FIG. 4, the number of wiring layers is set to three, but the number of wiring layers is not limited to three, and a structure in which a larger number of layers are laminated may be applied.

FIG. 5 is a plan view of the optical module mounting substrate 1000 when viewed from the first main surface side of the translucent substrate 100. The first wiring layer 200 is provided on the first main surface of the translucent substrate 100, the first opening 201 is formed inside the first wiring layer 200, and the peripheral portion of the first wiring layer is the first. It is covered with an insulating layer 210. In the first opening 201, the first main surface of the translucent substrate 100 is exposed.

FIG. 6 is a plan view of the optical module mounting substrate 1000 when viewed from the second main surface side of the translucent substrate 100. A second wiring layer 300 is provided on the second main surface of the translucent substrate 100, and a second opening 301 is formed inside the second wiring layer 300 at a position corresponding to the first opening 201. ing. In the second opening 301, the second main surface of the translucent substrate 100 is exposed. The outside of the second wiring layer 300 is surrounded by the second insulating layer 320, and the outside of the second insulating layer 320 is surrounded by the third insulating layer 340.

Next, a method of manufacturing the optical module mounting substrate 1000 will be described. First, as shown in the cross-sectional view of FIG. 7, a translucent substrate 100 having metal foils formed on both sides is prepared, and each metal foil is patterned. As a result, the first wiring layer 200 and the second wiring layer 300 are formed. As the translucent substrate 100, for example, polyimide can be used. The patterning of the first wiring layer 200 and the second wiring layer 300 is performed, for example, by supplying a photoresist to the surface of the metal foil, then exposing and developing a predetermined pattern, etching the exposed portion of the metal foil, and then the photoresist. It can be done by removing. As the metal foil, for example, copper, nickel, gold, tin, chromium, an alloy containing any of these, and the like can be used.

Next, the substrate adhesive layer 310 is supplied so as to surround the opening 301 and form a predetermined opening wider than the opening 301 on the surface on which the second wiring layer 300 is formed. Then, the second insulating layer 320 on which the metal foil to be the third wiring layer 330 is formed is bonded (FIG. 8). The substrate adhesive layer 310 can be supplied, for example, by a method of laminating a semi-cured sheet-like film, printing, dispensing, or the like.

Next, as shown in FIG. 9, the metal foil is patterned to form the third wiring layer 330. Here, at least in the region where the cavity structure is formed later, the third wiring layer 330 is patterned so as not to be arranged.

Next, the first insulating layer 210 is formed so as to cover a part of the first wiring layer 200 that does not include the opening 201. Further, the third insulating layer 340 is formed so as to cover a part of the region of the third wiring layer 330 (FIG. 10). The formation of the first insulating layer 210 and the third insulating layer 340 can be performed, for example, by using a screen printing method. In addition, a method of sticking a coverlay film having an opening at a predetermined position may be adopted.

When copper foil is used as the metal foil, nickel is applied to the surface of the first wiring layer 200 exposed from the first insulating layer 210 and the surface of the third wiring layer 340 exposed from the third insulating layer 340. A thin film may be formed in the order of gold. The thin film can be formed by, for example, an electroless plating method. Nickel functions as an anti-diffusion film, and gold contributes to surface oxidation prevention. Further, after forming a nickel thin film, a thin film may be formed in the order of palladium and gold. Further, although not shown, a through hole may be formed and each wiring layer may be connected. Connection using through holes can be performed, for example, by forming through holes penetrating each layer at predetermined positions by laser processing or the like, and forming a copper film on the side surface of the through holes by a plating method. Further, after forming the copper film, the center of the hole may be filled with an organic material.

Next, as shown in FIG. 11, the second insulating layer 320 in the region forming the cavity structure 350 is cut out. This processing can be performed by, for example, laser processing. At this time, the end portion of the region to be cut out is located on the second wiring layer 300. By doing so, since the second wiring layer 300 functions as a stopper layer for laser machining, the position of the bottom surface of the cavity structure 350 can be accurately controlled without any special ingenuity. From the above, the optical module mounting substrate 1000 is completed.

As described above, according to the present embodiment, the cavity structure can be easily and accurately formed on the optical module mounting substrate. In addition, by increasing the number of wiring layers to three or more layers, the wiring density per unit area can be increased, and driver ICs that control light emitting elements such as VCSELs and light receiving elements such as PDs, and other adjustment parts can be installed. Can be placed at high density on multi-layer wiring. Therefore, the optical module can be further miniaturized. Here, VCSEL is an abbreviation for Vertical Cavity Surface Emitting Laser, PD is an abbreviation for Photodiode, and IC is an abbreviation for Integrated Circuit. Further, at the bottom of the cavity structure, since the second wiring layer of the metal leaf is arranged at the bottom portion connected to the side wall of the cavity structure, the strength of the cavity structure is improved as compared with the case where the side wall is arranged at a position without wiring. be able to.
(Third embodiment)
In this embodiment, a specific example of an optical module using the optical module mounting substrate of the second embodiment will be described. FIG. 12 is a cross-sectional view showing the optical module 2000. In the optical module 2000, the optical element 400 is mounted on the first main surface side of the optical module mounting substrate 1000, and the lens plate 510 is mounted on the second main surface side.

As shown in FIG. 12, the optical element 400 is mounted face-down on the first wiring layer 200 of the optical module mounting substrate 1000. The optical functional unit 410 of the optical element 400 is positioned at the opening 201 of the first wiring layer 200. The first wiring layer 200 and the optical element 400 are connected via bumps 420 formed of Au, Cu, a solder material containing Sn as a main component, and the like. Further, the space between the optical element 400 and the translucent substrate 100 is protected by the sealing resin layer 430.

For the optical element 400, for example, a VCSEL which is a surface light emitting element, a PD which is a light receiving element, or the like can be used. When the optical element 400 is a light emitting element, the optical functional unit 410 is a light emitting unit, and when the optical element 400 is a light receiving element, the optical functional unit 410 is a light receiving unit.

The sealing resin layer 430 contributes to the protection of the connection portion by the bump 420 and the prevention of the presence of foreign matter. Here, the sealing resin layer 430 may be a material that transmits a predetermined wavelength, and may be a photocurable resin that undergoes a curing reaction with light having a wavelength such as visible light or ultraviolet light, a thermosetting resin, or a thermoplastic. Resin and the like can be applied. When the optical element 400 is a light receiving element, an optical signal incident from the cavity structure 350 side can pass through the translucent substrate 100 and the sealing resin layer 430 and be incident on the optical functional unit 410. When the optical element 400 is a light emitting element, the optical signal emitted from the optical functional unit 410 passes through the sealing resin layer 430 and the translucent substrate 100 and is emitted to the cavity structure 350 side.

A lens plate 510 is mounted on the second main surface side of the translucent substrate 100. A material such as glass or a polymer-based transparent member can be used for the lens plate 510, and the lens plate 510 may be formed by a molding method or the like. Further, the lens portion 511 formed on the lens plate 510 contributes to the light collection during transmission. The lens portion 511 of the lens plate 510 is housed in the cavity structure 350, and the first adhesive layer 520 is filled between the translucent substrate 100 and the lens plate 17. Further, the lens plate 510 is positioned so that the optical axis of the lens portion 511 passes through the opening 301 of the second wiring layer 300 and coincides with the optical axis of the optical function portion 410. The first adhesive layer 520 may be a material that transmits a predetermined wavelength, and for example, a refractive index matching agent or the like can be applied. Specifically, for example, a photocurable resin can be applied as the first adhesive layer 520. In this case, light having a predetermined wavelength can be applied from the back surface of the lens plate 510 to cure the lens.

In the above description, the structure in which one optical element 400 is mounted is shown on the first wiring layer, but the structure is not limited to this, and a plurality of optical elements 400 may be mounted. In this case, the lens plate 510 may have a structure having a lens portion 511 at a position facing each optical element 400.

As described above, according to the present embodiment, since an optical element having a three-dimensional shape such as a lens plate can be accommodated in the cavity structure, the optical module can be miniaturized. By arranging the lens portion in the cavity structure, the loss of the transmitted optical signal can be reduced and high transmission characteristics can be ensured.
(Fourth Embodiment)
In this embodiment, a modification of the optical module of the third embodiment will be described. FIG. 13 is a cross-sectional view showing the optical module 2100 of the present embodiment. The optical module 2100 has a structure in which the optical waveguide 600 is arranged on the back surface of the lens plate 510 of the optical module 2000 of the second embodiment. The optical waveguide 600 is adhesively fixed to the surface of the lens plate 510 opposite to the surface on which the lens portion 511 is arranged by a second adhesive layer 530. The optical waveguide 600 is composed of a core layer 610 and a clad layer 620 surrounding the core layer 610. Further, in the optical waveguide 600, a mirror portion 630 that bends the optical axis of the optical waveguide is arranged at a position facing the lens portion 511. The mirror portion 630 is formed so as to have an angle of 45 ° with respect to the optical axis of the optical waveguide 600. Then, the mirror unit 630 bends the optical signal transmitted from the core layer 610 by 90 ° and transmits the optical signal to the light receiving unit (optical function unit 410) of the optical element 400. Further, the optical signal transmitted from the light emitting unit (optical function unit 410) is bent by 90 ° and transmitted to the core layer 610 of the optical waveguide 600.

The second adhesive layer 530 may be a material that transmits a predetermined wavelength, and a refractive index matching agent or the like can be applied in the same manner as the first adhesive layer 520.

With the above configuration, the optical module can be made smaller than the configuration in which the optical waveguide is vertically connected to the second main surface of the translucent substrate.

The present invention has been described above by using the above-mentioned first to fourth embodiments as exemplary examples. However, the present invention is not limited to the above embodiment. That is, the present invention can apply various aspects that can be understood by those skilled in the art within the scope of the present invention.

Some or all of the above embodiments may also be described, but not limited to:
(Appendix 1)
Insulating translucent substrate and
A first wiring layer provided on the first main surface of the translucent substrate, the first opening is formed inside, and the first optical element is mounted on the upper surface.
A second wiring layer provided on the second main surface of the translucent substrate and having a second opening formed at a position corresponding to the first opening.
The surface of the second wiring layer is the first bottom surface, the second main surface of the translucent substrate exposed from the second opening is the second bottom surface, and the cavity structure is formed with itself as the side wall. A cavity wall that has a predetermined height and has a second optical element mounted on the top surface.
An optical module mounting board characterized by having.
(Appendix 2)
The optical module mounting substrate according to Appendix 1, wherein the second wiring layer is a metal foil.
(Appendix 3)
The optical module mounting substrate according to Appendix 1 or 2, wherein at least one of the first wiring layer and the second wiring layer has a multilayer structure having a wiring layer on the upper layer.
(Appendix 4)
The optical module mounting board according to any one of Supplementary note 1 to 3 and
The optical components housed in the cavity structure and
An optical module characterized by having.
(Appendix 5)
The optical module according to Appendix 4, wherein the optical component is a lens plate.
(Appendix 6)
The optical module according to Appendix 5, wherein an optical waveguide having a mirror portion for directing an optical axis to the lens plate is connected and fixed to the lens plate.
(Appendix 7)
The optical module according to any one of Supplementary note 4 to 6, wherein the optical element is mounted on the first wiring layer.
(Appendix 8)
A first opening is formed inside on the first main surface of the translucent substrate, and a first wiring layer on which the first optical element is mounted is formed on the upper surface.
A second wiring layer having a second opening formed at a position corresponding to the first opening on the second main surface of the translucent substrate is formed.
It is predetermined to form a cavity structure in which the surface of the second wiring layer is the first bottom surface, the second main surface of the translucent substrate exposed from the second opening is the second bottom surface, and the side wall is itself. Forming a cavity wall of height, on which the second optical element is mounted,
A method for manufacturing an optical module mounting board.
(Appendix 9)
The optical module mounting board is manufactured by the method for manufacturing the optical module mounting board described in Appendix 8.
A method for manufacturing an optical module, which comprises mounting an optical component housed in the cavity structure.
(Appendix 10)
The method for manufacturing an optical module according to Appendix 8 or 9, wherein the optical element is mounted on the first wiring layer.

1,100 Translucent substrate 2,200 1st wiring layer 2a, 201 1st opening 3,300 2nd wiring layer 3a, 301 2nd opening 4 Cavity wall 5,350 Cavity structure 10,1000 Optical module mounting substrate 210 1st insulating layer 310 Board adhesive layer 320 2nd insulating layer 330 3rd wiring layer 340 3rd insulating layer 400 Optical element 500 Optical component 510 Lens plate 600 Optical waveguide

Claims (10)

Insulating translucent substrate and
A first wiring layer provided on the first main surface of the translucent substrate, the first opening is formed inside, and the first optical element is mounted on the upper surface.
A second wiring layer provided on the second main surface of the translucent substrate and having a second opening formed at a position corresponding to the first opening.
The surface of the second wiring layer is the first bottom surface, the second main surface of the translucent substrate exposed from the second opening is the second bottom surface, and the cavity structure is formed with itself as the side wall. A cavity wall that has a predetermined height and has a second optical element mounted on the top surface.
An optical module mounting board characterized by having. The optical module mounting substrate according to claim 1, wherein the second wiring layer is a metal foil. The optical module mounting substrate according to claim 1 or 2, wherein at least one of the first wiring layer and the second wiring layer has a multilayer structure having a wiring layer on the upper layer. The optical module mounting substrate according to any one of claims 1 to 3.
The optical components housed in the cavity structure and
An optical module characterized by having. The optical module according to claim 4, wherein the optical component is a lens plate. The optical module according to claim 5, wherein an optical waveguide having a mirror portion for directing an optical axis to the lens plate is connected and fixed to the lens plate. The optical module according to any one of claims 4 to 6, wherein an optical element is mounted on the first wiring layer. A first opening is formed inside on the first main surface of the translucent substrate, and a first wiring layer on which the first optical element is mounted is formed on the upper surface.
A second wiring layer having a second opening formed at a position corresponding to the first opening on the second main surface of the translucent substrate is formed.
It is predetermined to form a cavity structure in which the surface of the second wiring layer is the first bottom surface, the second main surface of the translucent substrate exposed from the second opening is the second bottom surface, and the side wall is itself. Forming a cavity wall of height, on which the second optical element is mounted,
A method for manufacturing an optical module mounting board. The optical module mounting board is manufactured by the method for manufacturing the optical module mounting board according to claim 8.
A method for manufacturing an optical module, which comprises mounting an optical component housed in the cavity structure. The method for manufacturing an optical module according to claim 9, wherein an optical element is mounted on the first wiring layer.

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