Optical waveguide device

An optical waveguide device includes a wiring substrate, a connection pad formed in the wiring substrate, an optical waveguide in which a first cladding layer, a core layer, and a second cladding layer are formed of the wiring substrate in this order, an opening portion formed in the second cladding layer in a region including the connection pad, a contact hole formed at least in the first cladding layer on the connection pad, and being communicated with the opening portion of the second cladding layer, an optical element, including a connection terminal, connected to the connection pad through the contact hole, and underfill resin filled in the opening portion of the second cladding layer and the contact hole, and sealing a lower side of the optical element, wherein a part of the opening portion or the second cladding layer is exposed from the optical element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2013-242503, filed on Nov. 25, 2013, the entire contents of which are incorporated herein by reference.

FIELD

This invention is related to an optical waveguide device and a method of manufacturing the same.

BACKGROUND ART

Recently, the development of backbone communication lines mainly based on optical fiber communication technologies is proceeding steadily and, in such a situation, the transmission speeds of electric signals in electrical devices and information terminals are becoming a bottleneck. Against such background, instead of the conventional electric circuit substrate in which all signal transmissions are made by using the electric signal, the optoelectronic composite substrate of the type that transmits high-speed parts by the light has been proposed, in order to compensate the limit of transmission speed of the electric signal.

In the optoelectronic composite substrate, a light signal is transmitted by an optical waveguide which is constructed such that a core layer is surrounded by cladding layers. Then, an optical element is mounted on the cladding layer of the optical waveguide such that the optical element is optically coupled to the light path conversion mirror.

A related art is disclosed in Japanese Laid-open Patent Publication No. 2003-215371, Japanese Laid-open Patent Publication No, 2007-187871, Japanese Laid-open Patent Publication No. 2009-69668, and Japanese Laid-open Patent Publication No. 2010-277060.

SUMMARY

As will be explained in the preliminary matter section below, there is an optical waveguide device having a structure in which the connection terminals of an optical element are connected to connection pads in contact holes of a wiring substrate in a state that the lower face of the optical element touches the upper face of an optical waveguide. In such an optical waveguide device, it is difficult to pour the underfill resin into the contact holes, thus there is a problem that the sufficient reliability cannot be ensured.

According to one aspect discussed herein, there is provided an optical waveguide device, including a wiring substrate, a connection pad formed in the wiring substrate, an optical waveguide in which a first cladding layer, a core layer, and a second cladding layer are formed on the wiring substrate in this order, an opening portion formed in the second cladding layer in a region including the connection, pad, a contact hole formed at least in the first cladding layer on the connection pad, and the contact hole being communicated with the opening portion of the second cladding layer, an optical element including a connection terminal connected to the connection pad in the contact hole, and underfill resin filled in the opening portion of the second cladding layer and the contact hole, and underfill resin, sealing a lower side of the optical element, wherein a part of the opening portion of the second cladding layer is exposed from the optical element.

Also, according to another aspect discussed herein, there is provided a method of manufacturing an optical waveguide device, including preparing a wiring substrate including a connection pad on an upper face of the wiring substrate, forming a first cladding layer on the wiring substrate, forming a core layer on the first cladding layer,

forming a second, cladding layer on the first cladding layer and the core layer, the second cladding layer including an opening portion in a region including the connection pad, forming a contact hole at least in the first cladding layer, the contact hole being communicated with the opening portion of the second cladding layer and reaching the connection pad, connecting a connection terminal of an optical element, to the connection pad in the contact hole such that a part of the opening portion of the second cladding layer is exposed, and filling underfill resin into the contact hole through the opening portion of the second cladding layer, and sealing a lower side of the optical element.

Also, according to another aspect discussed herein, there is provided a method of manufacturing an optical waveguide device, including preparing a wiring substrate including a connection pad on an upper face of the wiring substrate, forming a first cladding layer on the wiring substrate, the first cladding layer including a contact hole on the connection pad, forming a core layer on the first cladding layer, forming a second cladding layer on the first cladding layer and the core layer, the second cladding layer including an opening portion being communicated with the contact hole, connecting a connection terminal of an optical element to the connection pad in the contact hole such that a part of the opening portion of the second cladding layer is exposed, and filling underfill resin into the contact hole through the opening portion of the second cladding layer, and sealing a lower side of the optical element.

The object and advantages of the invention will be realized and attained by means of the elements and combination particularly pointed out in the claims.

DESCRIPTION OF EMBODIMENTS

Hereinbelow, embodiments will be explained with reference to the accompanying drawings.

Prior to the explanation of embodiments, the preliminary matter to be set forth as a basis will be explained hereunder. As depicted inFIG. 1A, in an optical waveguide device according to the preliminary matter, an optical waveguide300is arranged on a wiring substrate100including wiring layers200. The optical waveguide300has a structure in which each core layer340is surrounded by a first cladding layer320and a second, cladding layer360.

A light path conversion mirror M is provided in an end part of the core layer340. Moreover, contact holes CH are formed in the first cladding layer320and the second cladding layer360and reach connection pads P of the wiring layers200.

Then, as depicted inFIG. 1B, connection terminals420of an optical element400are arranged in the contact holes CH and connected to the connection pads P of the wiring layers200through solder440. The optical element400is a light emitting element or a light receiving element, and the optical element400is optically coupled to the light path conversion mirrors M of the optical waveguide300.

Here, the height of each connection terminal420of the optical element400is set lower than the depth of each contact hole CH. By this matter, the lower face of the optical element400touches the upper face of the optical waveguide300, thereby a height position of the optical element400is decided, and most appropriate parallelism can be ensured.

In this state, since a space exists between each connection terminal420of the optical element400and the side wall of the contact hole CH, it is necessary to bury the space by the underfill resin. This is because, if the air remains inside the contact hole CH, the air expands in a subsequent heating process or the like, and the reliability of the electric connection of the optical element400decreases.

However, as depicted inFIG. 1B, since the lower face of the optical element400touches the upper face of the optical waveguide300, a problem arises that the underfill resin500cannot be poured into the contact hole CH.

In the case that there is a small gap on the lower face side of the optical element400, the underfill resin500can be filled therethrough, but doing so takes an extremely long process time and is not practical.

Embodiments to be explained below can solve the above-described problem.

Embodiment

FIG. 2AtoFIG. 10Bare views depicting a method of manufacturing an optical waveguide device of an embodiment.FIGS. 11A to 11Care views depicting an optical waveguide device of the embodiment. Hereinbelow, while explaining the method of manufacturing an optical waveguide device, a structure of the optical waveguide device will be explained.

In the method of manufacturing an optical waveguide device of the embodiment, first, a wiring substrate10as depicted inFIG. 2Ais prepared. In the wiring substrate10, wiring layers20are formed on both faces of a substrate12. Through-holes TH penetrating in the thickness direction are provided in the substrate12, and penetrating electrodes22are filled in the through-holes TH. The wiring layers20on both face sides are connected each other through the penetrating electrodes22. The wiring layer20on the upper face of the substrate12includes a connection pad P at one end thereof.

Also, a solder resist layer14is formed on the lower face of the substrate12, and the solder resist layer14in which opening portions14aare provided on connection parts of the wiring layers20.

Note that, the wiring layers20on both face sides may be connected each other by through-hole plating layers formed on the sidewalls of the through-holes TH, and resin may be filled in the remaining hole parts of the through-holes TH.

Also, the substrate12may be a rigid substrate or a flexible substrate. In the case of employing a rigid substrate, the substrate12is formed, for example, of glass epoxy resin or the like. Alternatively, in the case of employing a flexible substrate, the substrate12is formed, for example, of a polyimide film or the like. Moreover, on both face sides of the substrate12, the number of the lamination of wiring layers20can be set to any suitable number.

The through-holes TH in the wiring substrate10are formed by a drill, a laser, or the like, and the wiring layers20on both face sides and the penetrating electrodes22are formed by using the photolithography and plating techniques or the like.

Then, as depicted inFIG. 2B, a photosensitive resin layer (not depicted) for obtaining a first cladding layer is formed in an optical waveguide forming region on the wiring substrate10, and the exposure and the development are performed on the basis of the photolithography. Thereafter, the photosensitive resin layer is cured by a heating process at about 100° C. to 140° C. By this matter, a first cladding layer32is formed in the optical waveguide forming region on the wiring substrate10. The thickness of the first cladding layer32is about 10 μm to 30 μm, for example.

As the photosensitive resin layer, UV curable epoxy resin or the like is preferably used. As the method of forming the photosensitive resin layer, a semi-cured (B-stage) photosensitive resin sheet may be attached, or liquid photosensitive resin may be coated.

Similar resin is preferably used in later-described steps of forming a core layer and a second cladding layer.

Subsequently, as depicted inFIG. 3A, a photosensitive resin layer (not depicted) for obtaining the core layer is formed on the first cladding layer32. Further, the exposure and the development are performed on the basis of the photolithography, and then the photosensitive resin layer is cured by a heating process at about 100° C. to 140° C. By this matter, a core layer34is formed on the first cladding layer32.

In this step, as depicted in a plan view inFIG. 3B, the core layers34are formed side by side on the first cladding layer32as a plurality of belt-shaped patterns. The width of each core layer34is set to about 30 μm to 40 μm, and the thickness of each core layer34is set to about 30 μm to 80 μm.

FIG. 3Acorresponds to a cross section taken along broken line I-I in the plan view inFIG. 3B. The same applies toFIG. 4AtoFIG. 5Bto be mentioned later.

Thereafter, as depicted inFIGS. 4A and 4B, parts of on both end sides of each core layer34where light path conversion mirrors are to be arranged are cut in the thickness direction by the rotary blade of a cutting device.FIGS. 4A and 4Bdepict partially the region of the core layer34on one end side.

By this matter, Y-shaped dividing portions34aeach having a light path conversion inclined face S for converting a light path by 90° are formed. The light path conversion inclined face S is formed to incline preferably at 45° to the surface of the wiring substrate10. Besides the cutting, by using a laser or the like, the dividing portion.34ahaving the light path conversion inclined face S can be formed.

Furthermore, the dividing portion34amay be formed so as to divide the core layer34, and may be formed up to the halfway position in the thickness direction of the first cladding layer32.

Thereafter, as depicted inFIGS. 5A and 5B, a metal layer having a light reflective property is partially formed on the light path conversion inclined face S of each dividing portion34aof the core layer34by mask vapor deposition or the like, thereby a light path conversion mirror M is obtained. As the metal having the light reflective property, gold, aluminum, and the like are available.

Next, a method, of patterning a second cladding layer36on the first cladding layer32and the core layer34will be explained with reference toFIGS. 6A to 6C.FIG. 6Acorresponds to a cross section taken along broken line II-II in a plan view inFIG. 6C.FIG. 6Bcorresponds to a cross section taken along broken line III-III in the plan view inFIG. 6C.

The same applies toFIG. 7to be mentioned later. Also, the plan view inFIG. 6Cis illustrated in a perspective view, and the same applies to the subsequent plan views.

As depicted inFIG. 6A, a photosensitive resin layer (not depicted) for obtaining the second cladding layer is formed on the first cladding layer32and the core layer34. Further, the exposure and the development are performed on the basis of the photolithography, and then the photosensitive resin layer is cured by a heating process at about 100° C. to 140° C. By this matter, the second cladding layer36is formed on the first cladding layer32, the second cladding layer36covering the core layer34.

In this step, as depicted inFIG. 6C, the second cladding layer36is patterned such that opening portions36aare arranged in regions including the connection pads P of the wiring layers20of the wiring substrate10. Each opening portion36aof the second cladding layer36only needs to be arranged in a region including at least a part of the connection pad P.

As will be described later, the opening portions36aof the second cladding layer36function as flow paths for pouring the underfill resin into contact holes, after the connection terminals of an optical element are connected to the connection pads P inside the contact holes.

For this reason, the opening portions36aof the second cladding layer36are arranged so as to be communicated with the contact holes which are to be arranged on the connection pads P.

Moreover, the length of the opening portion36aof the second cladding layer36is set longer than the width of the optical element to be mounted. Thus, when the optical element is mounted, a part of the opening portion36aof the second cladding layer36is exposed outside the optical element.

In the example of the plan view inFIG. 6C, the diameter of the connection pad P of the wiring layer20is set larger than the width of the opening portion36aof the second cladding layer36. For example, the diameter of the connection pad P of the wiring layer20is 60 μm to 80 μm, and the width of the opening portion36aof the second cladding layer36is about 30 μm to 40 μm.

For this reason, in the example of the plan view inFIG. 6C, the opening portion36aof the second cladding layer36is arranged on the connection pad P such that the connection pad P protrudes from a sidewall of the opening portion36atoward an outside.

Alternatively, the diameter of the connection pad P may be made smaller than the width of the opening portion36aof the second cladding layer36, thereby the whole of the connection pad P may be arranged within the opening portion36aof the second cladding layer36.

Thereafter, as depicted inFIGS. 7A to 7C, the second cladding layer36and the first cladding layer32are processed by a laser to form contact holes CH reaching the connection pads P of the wiring layers20of the wiring substrate10.

As depicted inFIG. 7C, the contact hole CH is arranged on the connection pad P in a state that the contact hole C protrudes from the sidewall of the opening portion36aof the second cladding layer36toward the outside. The contact hole CH is formed so as to be communicated with the opening portion36aof the second cladding layer36.

By this matter, as depicted inFIG. 7A, an optical waveguide30in which the first cladding layer32, the core layers34and the second cladding layer36are formed in this order from the bottom is obtained on the wiring substrate10.

Note that, in the manufacturing method inFIG. 6AtoFIG. 7Cmentioned above, after the opening portions36aare formed in the second cladding layer36on the basis of the photolithography, end then the second cladding layer36and the first cladding layer32are opened by the laser to form the contact holes CH.

Besides this manufacturing method, as depicted inFIG. 8A, in the step inFIG. 2Bmentioned above, the contact holes CH may be formed in the first cladding layer32at the same time by the photolithography. Alternatively, after the step inFIG. 2Bmentioned above, the contact holes CH may be formed in the first cladding layer32by the laser.

Thereafter, as depicted inFIG. 8B, in the step inFIG. 6Bmentioned above, the opening portions36aare formed in the second cladding layer36so as to be communicated with the contact holes CH. By this matter, an optical waveguide30having the same structure as that inFIGS. 7A and 7Bcan be obtained.

In this method, the opening portion36aof the second cladding layer36on the region of the contact hole CH is formed to protrude toward the outside with a semicircle shape such that the opening portion36aconstitutes the sidewall of the contact hole CH.

Next, a method of mounting an optical element on the structure inFIGS. 7A to 7Cmentioned above will be explained with reference toFIGS. 9A to 9C. Similarly toFIGS. 6A to 6Cmentioned above,FIG. 9Acorresponds to a cross section taken along broken line IV-IV in a plan view inFIG. 9C, andFIG. 9Bcorresponds to a cross section taken along broken line V-V in the plan view inFIG. 9C. The same applies toFIGS. 10A to 10CandFIGS. 11A to 11Cto be mentioned later. Also,FIG. 9Cis illustrated in a perspective view.

As depicted inFIG. 9B, an optical element40including connection terminals42on a lower face thereof is prepared. The connection terminals42are formed of a bump electrode such as a gold bump. Then, the connection terminals42of the optical element40are connected to the connection pads P of the wiring layers20in the contact holes CH through solder44.

In the case that the optical element40is a light emitting element, it includes light, emitting portions40ain the lower face, and the light emitting portions40aare optically coupled to the light path conversion mirrors M of the core layers34. Alternatively, in the case that the optical element40is a light receiving element, it includes light receiving portions40bin the lower face, and the light receiving portions40bare optically coupled to the light path conversion mirrors M of the core layers34.

Here, referring to the plan view inFIG. 9C, as mentioned above, the length of the opening portions36aof the second cladding layer36, which are communicated with the contact holes CH, is set longer than the width of the optical element40. For this reason, when the optical element40is mounted, it is in a state that parts of the both end sides of each opening portion36aof the second cladding layer36are exposed outside the optical element40respectively.

Also, the height of the connection terminal42of the optical element40is set lower than the height from the surface of the connection pad P located at the bottom of the contact hole CH to the upper end of the opening portion36aof the second cladding layer36. For this reason, as depicted, inFIG. 9A, the lower face of the optical element40touches the upper face of the second cladding layer36, thereby the height position of the optical element40is decided, and most appropriate parallelism can be ensured.

In this way, in the state that the lower face of the optical element40touches the upper face of the second cladding layer36, the opening portions36aof the second cladding layer36, which are used as the flow paths of the underfill resin, are exposed outside the optical element40and are arranged.

Thereafter, as depicted inFIGS. 10A and 10B, liquid underfill resin is coated to the vicinity region of the side faces of the optical element40in a lump by a dispenser or the like. In this step, the underfill resin infiltrates by the capillary action up to the inside of the contact holes CH which are communicated with the opening portions36a, in a state that the opening portions36aof the second cladding layer36function as the flow path.

By this matter, as depicted inFIGS. 11B and 11C, the underfill resin50is filled in the opening portions36aof the second cladding layer36under the optical element40and in the gaps between the side faces of the contact holes CH which are communicated with the opening portions36aand the connection terminals42of the optical element40.

In the plan view inFIG. 11C, the underfill resin50is filled in the regions hatched with oblique lines. Moreover, as depicted inFIG. 11A, in the parts that the optical element40touches the second cladding layer36, it is in a state that the underfill resin50remains on both outer sides of the optical element40.

In this way, in this embodiment, even when the optical element40is mounted such that the lower face of the optical element40touches the upper face of the second cladding layer36, the parts of the opening portions36aof the second cladding layer36, which are communicated with the contact holes CH, are exposed outside the optical element40. For this reason, the underfill resin50can be easily filled from the opening portions36aof the second cladding layer36into the contact holes CH under the optical element40.

By the above steps, as depicted inFIGS. 11A to 11C, an optical waveguide device1of the embodiment is obtained.

As depicted inFIGS. 11A and 11B, the optical waveguide device1of the embodiment includes the wiring substrate10explained inFIG. 2Amentioned above. The optical waveguide30is formed on the wiring substrate10.

The optical waveguide30is formed from the first cladding layer32, the core layers34formed on first cladding layer32, and the second cladding layer36covering the core layers34, and has a structure in which the core layers34are surrounded by the first and second cladding layers32,36. The refractive index of the core layer34is set higher than the refractive indexes of the first cladding layer32and the second cladding layer36.

As depicted inFIGS. 11B and 11C, the contact holes CH are formed in the second cladding layer36and the first cladding layer32and reach the connection pads F of the wiring layers20. Further, the opening portions36aare formed in the second cladding layer36in the regions including the connection pads P, and are communicated with the contact holes CH.

The opening portions36aof the second cladding layer36are communicated with the contact holes CH respectively, and are arranged to be separated each other, and are formed to extend with a long and narrow shape in the same direction as the extending direction of the core layers34.

Then, the connection terminals42of the optical element40are arranged in the contact holes CH, and are connected to the connection pads P of the wiring layers20through the solder44.

The length of the opening portion36aof the second cladding layer36is set longer than the width of the optical element40, and the parts or the opening portions36aof the second cladding layer36protrude and are exposed to both outer sides of the optical element40.

Moreover, the height of the connection terminal42of the optical element40is set lower than the height from the surface of the connection pad P located at the bottom of the contact hole CH to the upper end of the opening portion36aof the second cladding layer36. For this reason, the lower face of the optical element40touches the upper face of the second cladding layer36, thereby the height position of the optical element40is decided, and most appropriate parallelism can be ensured.

Further, as depicted inFIGS. 11B and 11C, the underfill resin50for sealing the lower side of the optical element40is filled in the opening portions36aof the second cladding layer36and in the gaps between the sidewalls of the contact holes CH and the connection terminals42of the optical element40.

A light emitting element or a light receiving element is used as the optical element40. A vertical cavity surface emitting laser (VCSEL) is preferably used as the light emitting element, and a photodiode is preferably used as the light receiving element.

Moreover, as depicted inFIG. 11A, the light path conversion mirrors M formed of the metal having the light reflective property are arranged in the end parts of the core layers34of the optical waveguide30. Then, the optical element40is optically coupled to the light path conversion mirrors M of the optical waveguide30.

In the case that the optical element40is a light emitting element, the light emitting portions40aarranged in the lower face of the light emitting element are optically coupled to the light path conversion mirrors M. Alternatively, in the case that the optical element40is a light receiving element, the light receiving portions40barranged in the lower face of the light receiving element are optically coupled to the light path conversion mirrors M.

As described above, in the optical waveguide device1of the embodiment, the underfill resin50is filled into the contact holes CH, in a state that the opening portions36aof the second, cladding layer36arranged outside the optical, element40function as the flow paths.

Since each contact hole CH is communicated with the opening portions36aof the second cladding layer36, the underfill resin50can be filled reliably into all the contact holes CH. By this matter, even if a heating process is performed later, the air never expands inside the contact holes CH. By this matter, it is possible to ensure the reliability of the electric connection between the optical element40and the connection pad P of the wiring substrate10.

Moreover, when the optical element40is mounted, the lower face of the optical element40is touched to the upper face of the optical waveguide30. Therefore, the height level and the parallelism can be optimized easily, and the optical performance can be improved.

FIG. 12depicts a state that a control element60is connected to the optical element40inFIG. 11A. As depicted inFIG. 12, a solder resist layer15is formed on the wiring substrate10at a lateral side of the optical element40, the solder resist layer15in which opening portions15aare provided on the connection parts of the wiring layers20.

Then, connection terminals62of the control element60are connected to the connection parts of the wiring layers20through solder64. Further, underfill resin50ais filled under the control element60.

In this way, the optical element40is electrically connected to the control element60through the wiring layers20of the wiring substrate10.

Next, light propagation in the optical waveguide device1of the embodiment will be explained with reference toFIGS. 11A and 11BandFIG. 12. InFIG. 12, in the case that the optical element40is a light emitting element, the control element60is arranged as a driver element. Then, electric signals outputted from the driver element are supplied to the light emitting element, and light is emitted downward from the light emitting face of the light emitting element.

The light emitted from the light emitting element is transmitted through the second cladding layer36and reaches the light path conversion mirrors M (FIG. 11A). Further, the light is reflected by the light path conversion mirrors M, thereby the light paths are converted by 90°, and the light enters the core layers34.

Thereafter, the light entered in the core layers34propagates inside the core layers34by repeating total internal reflection, and the light paths are converted by 90° C. at the light path conversion mirrors M on the other end side. And then the light enters the light receiving portions of a light receiving element.

On the other hand, in the case that the optical element40is a light receiving element, the control element60is arranged as an amplifier element. In this case, the light propagates in the directions reverse to the light path described above, and the light enters the light receiving face of the light receiving element. Further, the optical signals are converted into electric signals by the light receiving element, and the electric signals are supplied to the amplifier element.

Other Embodiments

FIG. 13toFIG. 15are plan views depicting modifications of the opening portions36aof the second cladding layer36inFIGS. 7A to 7Cmentioned above. InFIGS. 7A to 7Cmentioned above, each one of the opening portions36aof the second cladding layer36is communicated with one contact hole CH and is arranged to be separated each other.

As depicted in a first modification inFIG. 13, end parts of two adjacent opening portions36aof the second cladding layer36inFIG. 7Cmay be connected each other, so that one opening portion36bin a “U-shape” is communicated with two contact holes CH.

Moreover, like a second modification inFIG. 14, one end of each separated opening portion36aof the second cladding layer36inFIG. 7Cmay be connected to a common opening portion arranged along the longitudinal direction, so that one continuous opening portion36cin a comb-shaped pattern is communicated with all the contact holes CH.

Furthermore, like a third modification inFIG. 15, one lump opening portion36dof the second cladding layer36may be arranged in the vicinity of two contact holes CH arranged at one end side of one core layer34. In this case, the whole of two contact holes CH are arranged within one opening portion36dof the second cladding layer36, and the contact holes CH are formed only in the first cladding layer32.

In this way, as illustrated inFIGS. 7A to 7CandFIG. 13toFIG. 15, one opening portion of the second cladding layer36may be communicated with one contact hole CH or with a plurality of contact holes. That is, the opening portions of the second cladding layer36are communicated with the contact holes CH such that the opening portions do not interfere with the optical waveguide30, therefore the opening portion can adopt various shapes.

The opening portions36aof the second cladding layer36are communicated with the contact holes CH. By this matter, the underfill resin50can be filled into the contact holes CH in a state that the opening portions36aof the second cladding layer36function as the flow paths.

Further, the clauses are disclosed about, the above embodiment hereinafter.

(Clause 1) A method of manufacturing an optical waveguide device, comprising:

preparing a wiring substrate including a connection pad on an upper race of the wiring substrate;

forming a first cladding layer on the wiring substrate;

forming a core layer on the first cladding layer;

forming a second cladding layer on the first cladding layer and the core layer, the second cladding layer having an opening portion in a region including the connection pad;

forming a contact hole at least in the first cladding layer, the contact hole being communicated with the opening portion of the second cladding layer and reaching the connection pad;

connecting a connection terminal of an optical element to the connection pad through the contact hole such that a part of the opening portion of the second cladding layer is exposed; and

filling underfill resin into the contact hole through the opening portion of the second cladding layer, and sealing a lower side of the optical element.

(Clause 2) A method of manufacturing an optical waveguide device, comprising;

preparing a wiring substrate including a connection pad on an upper face of the wiring substrate;

forming a first cladding layer on the wiring substrate, the first cladding layer including a contact hole on the connection pad;

forming a core layer on the first cladding layer;

forming a second cladding layer on the first cladding layer and the core layer, the second cladding layer including an opening portion being communicated with the contact hole;

connecting a connection terminal of an optical element to the connection pad in the contact hole such that a part of the opening portion of the second cladding layer is exposed; and

filling underfill resin into the contact hole through the opening portion of the second cladding layer, and sealing a lower side of the optical element.

(Clause 3) The method of manufacturing an optical waveguide device according to Clause 1, wherein, in the connecting of the optical element, a lower face of the optical element is touched to an upper face of the second cladding layer.

(Clause 4) The method of manufacturing an optical waveguide device according to Clause 1, wherein

One of the opening portion of the second cladding layer is communicated with one of the contact hole, or a plurality of the contact holes.

(Clause 5) The method of manufacturing an optical waveguide device according to Clause 1, wherein

the optical element is any one of a light emitting element and a light receiving element, and

further comprising mounting a control element on the wiring substrate, the control element being electrically connected to the optical element.