JP2018159728A - Photoelectric wiring board, electronic apparatus, and method for manufacturing photoelectric wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical electrical wiring board and an electronic device capable of enhancing electrical connection reliability and optical transmission characteristics. An optical electrical wiring board 100 includes a substrate 1, an electrode portion 2, a first clad layer 3a, a solder resist layer 4, a core portion 3b, and a second clad layer 3c. The substrate has a first surface 1a. The electrode portion 2 is arranged on the first surface. Further, the electrode portion has a second surface 2a on the opposite side to the substrate. The first clad layer is arranged so as to expose the second surface on the first surface. Further, the first clad layer has a third surface 3aa on the side opposite to the substrate. The solder resist layer is arranged from the second surface to the end of the third surface. The core portion is arranged on the portion of the third surface whose distance from the second surface is farther than the end portion. The second clad layer covers the core portion. [Selection diagram] Fig. 2

Description

  The present disclosure relates to an opto-electric wiring board including an optical waveguide and a wiring conductor, and an electronic device using the same.

  In recent years, it has been studied to perform signal transmission between electronic devices using light for the purpose of improving information processing capability. Therefore, an optoelectric wiring board has been developed in which an optical waveguide for transmitting an optical signal by converting an electrical signal of an electronic device into an optical signal is formed.

  An example of such an opto-electric wiring board is described in Patent Document 1. This optoelectric wiring board has an optical waveguide and an electrode on the wiring board. This optical waveguide has a clad layer and a core layer. The electrode is for mounting an optical element or the like, and is connected to a wiring conductor provided on the wiring board via a through conductor penetrating the cladding layer.

JP 2011-118163 A

  In an optoelectric wiring board and an electronic device using the same, it is desired to improve both electrical connection reliability and optical transmission characteristics. The present disclosure has been devised in view of such circumstances, and an object thereof is to provide an opto-electric wiring board and an electronic device that can improve electrical connection reliability and optical transmission characteristics.

  An optoelectric wiring board according to an embodiment of the present invention includes a substrate, an electrode portion, a first cladding layer, a solder resist layer, a core portion, and a second cladding layer. The substrate has a first surface. The electrode portion is disposed on the first surface. Moreover, the electrode part has the 2nd surface on the opposite side to a board | substrate. The first cladding layer is disposed on the first surface so as to expose the second surface. The first cladding layer has a third surface opposite to the substrate. The solder resist layer is arranged from the second surface to the end of the third surface. The core portion is disposed on a portion of the third surface that is farther from the second surface than the end portion. The second cladding layer covers the core part.

  An electronic device according to an embodiment of the present invention includes the above-described optoelectric wiring board and an optical element connected to the second surface via a connection member.

  The manufacturing method of the optoelectric wiring board according to an embodiment of the present invention includes the following steps. Preparing a substrate having a first surface; Providing an electrode part having a second surface opposite to the substrate on the first surface; Providing a first cladding layer having a third surface opposite to the substrate on the first surface so that the second surface is exposed; A step of providing a solder resist layer from the second surface to the end of the third surface. A step of providing a core part and a second cladding layer covering the core part on a part of the third surface that is farther from the end part than the end part.

  According to each of the above embodiments, electrical connection reliability and optical transmission characteristics can be improved in the opto-electric wiring board and the electronic device.

It is a top view of the optoelectric wiring board of a 1st embodiment. (A) is sectional drawing in the II-II line of the optoelectronic wiring board of FIG. 1, (b) is sectional drawing of the electronic apparatus which mounted the optical element in the optoelectronic wiring board of (a). (A) is sectional drawing in the III-III line of the optoelectronic wiring board of FIG. 1, (b) is sectional drawing of the electronic apparatus which mounted the optical element in the optoelectronic wiring board of (a). (A) is sectional drawing of the optoelectronic wiring board of 2nd Embodiment, (b) is sectional drawing of the electronic device of the electronic device which mounted the optical element on the optoelectronic wiring board of (a). (A) is sectional drawing of the optoelectronic wiring board of 2nd Embodiment, (b) is sectional drawing of the electronic device of the electronic device which mounted the optical element on the optoelectronic wiring board of (a). (A)-(e) is sectional drawing which shows the state in the middle of a manufacturing process in an example of the manufacturing method of an optoelectronic wiring board. (A)-(e) is sectional drawing which shows the state in the middle of a manufacturing process in the other example of the manufacturing method of an optoelectric wiring board.

  The optoelectric wiring board and the electronic device of the present disclosure will be described with reference to the drawings. Although any direction of the opto-electric wiring board and the electronic device may be upward, in the present disclosure, for the sake of convenience, an orthogonal coordinate system (X, Y, Z) is defined, and the positive direction in the Z-axis direction is defined. The side may be described as being upward.

  1 to 3 show an optoelectric wiring board 100 according to the first embodiment. FIG. 1 is a plan view of the optoelectric wiring board 100. 2A is a cross-sectional view taken along line II-II of the optoelectronic wiring board 100 of FIG. FIG. 3A is a cross-sectional view taken along the line III-III of the optoelectronic wiring board 100 of FIG. By mounting the optical element 6 on the optoelectronic wiring board 100, the electronic device 101 shown in FIGS. 2B and 3B is obtained. 2B and 3B are cross-sectional views at the same positions as those in FIGS. 2A and 3A, respectively. The electronic device 101 is mounted on a product such as an optical transceiver, a server, or a router, for example.

  The optoelectric wiring board 100 has a function of transmitting optical signals and electrical signals. The optoelectric wiring board 100 includes a substrate 1, an electrode part 2, a first cladding layer 3a, a solder resist layer 4, a core part 3b, and a second cladding layer 3c. The first cladding layer 3a, the core portion 3b, and the second cladding layer 3c function as the optical waveguide 3.

  The substrate 1 has a first surface (upper surface) 1a, and supports the optical element 6 and the optical waveguide 3 on the first surface. The substrate 1 includes, for example, a plurality of insulating layers (not shown), a plurality of metal layers (not shown), and via conductors (not shown). The plurality of insulating layers and the plurality of metal layers are alternately stacked. The via conductor is provided so as to penetrate through one insulating layer, and the metal layers adjacent in the vertical direction are electrically connected to each other via the via conductor. Note that the metal layer functions as a wiring conductor of the substrate 1. The substrate 1 can be manufactured by a conventionally known method.

  The substrate 1 is not limited to having a plurality of insulating layers and a plurality of metal layers. The substrate 1 may have, for example, one insulating layer and a metal layer disposed on the upper surface of the one insulating layer. Moreover, the board | substrate 1 may have a laminated body which consists of a some insulating layer, and the metal layer distribute | arranged to the upper surface of the laminated body, for example. Moreover, the board | substrate 1 may mix and laminate | stack the insulating layer and the laminated body which consists of a some insulating layer, for example.

  For the insulating layer of the substrate 1, for example, a resin material such as an epoxy resin or a ceramic material such as silica, alumina, or zirconia is used. The metal layer and via conductor of the substrate 1 are made of, for example, a metal material such as copper or aluminum.

  The electrode unit 2 is disposed on the first surface 1 a of the substrate 1. The electrode unit 2 has a second surface (upper surface) 2 a opposite to the substrate 1. The electrode portion 2 is for electrically connecting the wiring conductor of the substrate 1 and the optical element 6. For example, a metal material such as copper or aluminum is used for the electrode portion 2.

  The solder resist layer 4 is for protecting the surface of the substrate 1. The solder resist layer 4 is made of an insulating material capable of maintaining good insulation even in a heating process when the optical element 6 is connected via a connecting member 7 such as solder. Examples of such an insulating material include a resin material such as an epoxy resin. From the viewpoint of maintaining better electrical connection between the electrode portion 2 and the wiring conductor provided on the substrate 1, the solder resist layer 4 has, for example, an inorganic filler of 40 vol% or more and 70 vol% or less. May be. As the inorganic filler, for example, silica particles or alumina particles having an average particle diameter of 0.1 μm to 2 μm are used.

  As shown in FIGS. 2 and 3, the solder resist layer 4 exposes at least a part of the second surface 2a of the electrode portion 2, and from the second surface 2a, a third surface of the first cladding layer 3a described later. (Upper surface) It is arranged over the end 3A of 3aa. The end portion 3A of the third surface 3aa of the first cladding layer 3a is a portion located in the vicinity of the second surface 2a of the electrode portion 2 in the third surface 3aa of the first cladding layer 3a.

  The optical waveguide 3 has a function of transmitting an optical signal. The optical waveguide 3 has a first cladding layer 3a, a strip-shaped core portion 3b, and a second cladding layer 3c. Since the refractive index of the core portion 3b is set to be larger than the refractive indexes of the first cladding layer 3a and the second cladding layer 3c, the light that has entered the core portion 3b is reflected in the core portion 3b and the first cladding layer 3a. And the inside of the core portion 2b while repeating reflection at the interface between the core portion 3b and the second clad layer 3c. As a result, the optical waveguide 3 can transmit an optical signal.

  The refractive index of the core part 3b is set to 1.5 or more and 1.6 or less, for example. The refractive indexes of the first cladding layer 3a and the second cladding layer 3c are set to 1.45 or more and 1.55 or less, for example. The refractive index of the core portion 3b is, for example, in the range of 0.1% to 0.5% with respect to the refractive indexes of the first cladding layer 3a and the second cladding layer 3c, and the first cladding layer 3a and the second cladding layer. It is set larger than the refractive index of 3c.

  The first cladding layer 3a is a layered body. The first cladding layer 3 a is disposed on the first surface 1 a of the substrate 1 so as to expose the second surface 2 a of the electrode portion 2. The first cladding layer 3 a has a third surface 3 aa opposite to the substrate 1. The thickness of the first cladding layer 3a (the length in the Z direction in FIGS. 2 and 3) is, for example, not less than 10 μm and not more than 100 μm. As the first clad layer 3a, for example, an epoxy resin, a polyimide resin, a phenol resin, an acrylic resin, or the like can be used.

  As shown in FIGS. 2 and 3, the first cladding layer 3 a may be in contact with the outer edge portion of the second surface 2 a of the electrode portion 2. With such a configuration, there is no gap between the electrode portion 2 and the first cladding layer 3 a, and bubbles are less likely to be generated in the solder resist 4 when the solder resist layer 4 is formed. As a result, the solder resist layer 4 is hardly cracked.

  Further, the first cladding layer 3a may surround the electrode portion 2 when viewed in plan. With such a configuration, even when the electrode part 2 is disposed in the vicinity of the optical waveguide 3 and the optoelectric wiring board 100 is downsized, the adhesion between the first cladding layer 3a and the substrate 1 is maintained well. it can.

  Further, in such a configuration, a portion where the solder resist layer 4 and the first cladding layer 3a overlap may surround the electrode portion 2. With such a configuration, by surrounding the electrode 2 with the same material, distortion due to thermal expansion or the like hardly occurs.

  The core part 3b is a strip-like body extending in the X-axis direction. The core portion 3b is disposed on a portion of the third surface 3aa where the distance from the second surface 2a of the electrode portion 2 is farther than the end portion 3A. The thickness of the core part 3b (the thickness in the Z direction in FIGS. 2 and 3) is, for example, 20 μm or more and 50 μm or less, and the width of the core part 3b (the length in the Y-axis direction in FIG. 1) is, for example, 20 μm or more and 50 μm or less. It is. For example, an epoxy resin or the like can be used as the core portion 3b.

  The second cladding layer 3c covers the upper surface and side surfaces of the core portion 3b. The thickness of the second cladding layer 3c (the length in the Z direction in FIGS. 2 and 3) is, for example, not less than 10 μm and not more than 100 μm. As the second clad layer 3c, for example, an epoxy resin, a polyimide resin, a phenol resin, an acrylic resin, or the like can be used.

  Similar to the core portion 3b, the second cladding layer 3c is disposed on a portion of the third surface 3aa where the distance from the second surface 2a of the electrode portion 2 is farther than the end portion 3A. That is, the first cladding layer 3a protrudes more toward the electrode part 2 than the core part 3b and the second cladding layer 3c, and the end part 3A covered with the solder resist layer 4 on the protruding first cladding layer 3a. Is located.

  With such a configuration, it is possible to improve electrical connection reliability and optical transmission characteristics in the optoelectric wiring board 100 and the electronic device 101. That is, the solder resist layer 4 covers a part of the optical waveguide 3 so that the optical waveguide 3 is firmly fixed to the substrate 1 with the solder resist layer 4 and peeled even if the heat resistance of the optical waveguide 3 is relatively low. Can be difficult. Further, since the solder resist layer 4 covers only the first cladding layer 3 a in the vicinity of the electrode portion 2, the level difference of the portion covered by the solder resist 4 is reduced, and the optical waveguide 3 and the solder resist 4 are separated. The stress due to the difference in thermal expansion coefficient can also be reduced. From the above, the electrical connection reliability can be increased by protecting the part having electrical conductivity such as the electrode part 2 with the solder resist layer 4 excellent in heat resistance and insulation. In addition, the optical waveguide 3 can be made to have a high optical transmission property by preferentially adopting a material having an excellent optical transmission property. Then, by covering a part of the optical waveguide 3 with the solder resist layer 4, the heat resistance of the optical waveguide 3 can be compensated and the optical waveguide 3 can be stably maintained.

  The mirror part 5 is arranged on a part of the optical waveguide 3 and is for optically connecting the optical element 6 and the core part 3b. The mirror part 5 is inclined with respect to the extending direction (X-axis direction) of the core part 3b, and the inclined surface is a light reflecting surface. That is, the mirror unit 5 can guide light into the core unit 3b by reflecting light emitted downward (−Z direction) from the optical element 6 in the plane direction (+ X direction). Alternatively, the mirror unit 5 can guide the light to the optical element 6 by reflecting the light emitted from the core unit 3 b in the plane direction (−X direction) upward (+ Z direction). The mirror part 5 can be formed by cutting out a part of the optical waveguide 3 using dicing, laser processing or the like.

  In addition, between the mirror part 5 and the core part 3b, the translucent resin which has a light transmittance with respect to the light transmitted between these may be filled. As such a translucent resin, for example, an epoxy resin or a silicone resin can be used. The refractive index of the translucent resin may be smaller than the refractive index of the core portion 3b. With such a configuration, an optical signal can be transmitted favorably between the mirror unit 5 and the core unit 3b. In addition, the refractive index of translucent resin is set to 1.45 or more and 1.55 or less, for example.

  By mounting the optical element 6 on the optoelectronic wiring board 100, the electronic device 101 shown in FIGS. 2B and 3B is obtained. The optical element 6 may be a light emitting element that converts an electrical signal into an optical signal, or may be a light receiving element that converts an optical signal into an electrical signal. The optical element 6 is electrically connected to the electrode 2 of the optoelectric wiring board 100 via a bonding member 7 such as solder, for example.

  Various light emitting elements or light receiving elements can be applied to the optical element 6. As the light emitting element, for example, a vertical cavity surface emitting laser (VCSEL) can be used. Moreover, as a light receiving element, a photodiode (PD: Photo Diode) etc. can be used, for example. Alternatively, the optical element 6 may be a light receiving / emitting element having both a light emitting part and a light receiving part.

  The optical element 6 is mounted on the optoelectric wiring board 100 so that the light emitting part 6 a or the light receiving part 6 a faces the mirror part 5. With such a configuration, the optical element 6 and the mirror unit 5 can be brought close to each other, and the optical waveguide 3 and the optical element 6 can be optically coupled with low loss.

  A method for manufacturing the optoelectric wiring board 100 of the first embodiment will be described below.

  First, as shown in FIG. 6A, the electrode unit 2 is formed on the first surface 1a of the substrate 1 by using a photolithography technique or the like. Thereafter, as shown in FIG. 6B, the first cladding layer 3a is formed by using a photolithography technique or the like so as to expose the second surface 2a of the electrode portion 2.

  Next, as shown in FIG. 6C, the solder resist layer 4 is formed so as to be continuous from the second surface 2a of the electrode portion 2 to the end portion 3A of the third surface 3a of the first cladding layer 3a. It is produced using a lithography technique or the like.

  Next, as shown in FIG. 6D, the second portion that covers the core portion 3b and the core portion 3b on the portion of the third surface 3aa that is located farther from the end portion 3A than the end surface 3A. The clad layer 3c is produced using a photolithography technique or the like.

  As described above, when the core portion 3b and the second cladding layer 3c are formed after the solder resist layer 4 is formed to form the optical waveguide 3, the external force received by the optical waveguide 3 during the manufacturing process is reduced. 3 The dimensional accuracy of the optical waveguide 3 can be maintained satisfactorily, and the optical transmission characteristics can be enhanced.

  Next, as shown in FIG. 6E, a part of the optical waveguide 3 is cut out by using a dicing process or the like, thereby forming a mirror portion 5 having an inclined surface. On the inclined surface of the mirror unit 5, a light reflection rate may be increased by depositing a metal layer by plating or the like. As described above, the optoelectric wiring board 100 of the first embodiment can be manufactured.

  The manufacturing method of the optoelectronic wiring board 100 of the first embodiment is not limited to the above manufacturing method, and various modifications are possible. A modification is shown below.

  First, as shown in FIG. 7A, the electrode unit 2 is formed on the first surface 1a of the substrate 1 by using a photolithography technique or the like. Thereafter, as shown in FIG. 7B, the first cladding layer 3a is formed by using a photolithography technique or the like so as to expose the second surface 2a of the electrode portion 2.

  Next, as shown in FIG. 7C, the core portion 3b and the core portion 3b are disposed on the portion of the third surface 3aa at a position farther from the end portion 3A of the first cladding layer 3a. The second cladding layer 3c that covers the core portion 3b is produced using a photolithography technique or the like.

  Next, as shown in FIG. 7 (d), the solder resist layer 4 is continuously applied from the second surface 2a of the electrode portion 2 to the end portion 3A of the first cladding layer 3a by using a photolithography technique or the like. To make.

  Thus, the solder resist layer 4 may be formed after forming the core portion 3b and the second clad layer 3c to form the optical waveguide 3. In this case, since there is no solder resist layer 4 when the core portion 3b and the second cladding layer 3c are formed on the first cladding layer 3a, the core layer 3b and the second cladding layer 3c can be easily formed, and the first cladding Adhesion with the layer 3 can be enhanced.

  Next, as shown in FIG. 7E, a part of the optical waveguide 3 is cut out by using dicing, laser processing or the like, thereby forming a mirror portion 5 having an inclined surface. On the inclined surface of the mirror unit 5, a light reflection rate may be increased by depositing a metal layer by plating or the like. As described above, the optoelectric wiring board 100 of the first embodiment can be manufactured. The mirror portion 5 may be formed before the solder resist layer 4 is formed.

  The optoelectric wiring board and the electronic device of the present disclosure are not limited to the above-described embodiments, and various changes and improvements can be made without departing from the gist of the present disclosure. For example, the following other embodiments may be used.

  4 and 5 show an optoelectric wiring board 200 of the second embodiment. FIG. 4A is a cross-sectional view of the optoelectronic wiring board 200, showing a cross section at the same position as the cross section of the optoelectronic wiring board 100 of FIG. 4B is a cross-sectional view of the electronic device 201, and shows a cross section at the same position as the cross section of the electronic device 101 in FIG. 5A is a cross-sectional view of the optoelectronic wiring board 200, and shows a cross section at the same position as the cross section of the optoelectronic wiring board 100 of FIG. 5B is a cross-sectional view of the electronic device 201, and shows a cross section at the same position as the cross section of the electronic device 101 in FIG.

  The optoelectric wiring board 200 includes a substrate 21 having a first surface 21a, an electrode portion 22 having a second surface 22a, a first cladding layer 23a having a third surface 23aa, a solder resist layer 24, and a core portion 23b. And a second cladding layer 23c. The first cladding layer 23 a, the core portion 23 b, and the second cladding layer 23 c function as the optical waveguide 23.

  As in the optoelectric wiring board 100 of the first embodiment, the optoelectric wiring board 200 has the solder resist layer 24 disposed from the second surface 22a to the end 23A of the third surface 23aa. As a result, the electrical connection reliability and optical transmission characteristics of the optoelectric wiring board 200 can be improved. On the other hand, the opto-electric wiring board 200 is different from the opto-electric wiring board 100 in that the first cladding layer 23 a is separated from the electrode portion 22. In the case of such a configuration, the solder resist layer 24 can be stably formed on the electrode portion 22.

  Similar to the photoelectric wiring substrate 100 of the first embodiment, the photoelectric wiring substrate 200 becomes the electronic device 201 by mounting the optical element 26 on the electrode portion 2 via a bonding member 27 such as solder. The optical element 26 is mounted on the optoelectric wiring board 200 such that the light emitting portion 26 a or the light receiving portion 26 a faces the mirror portion 25. With such a configuration, the optical element 26 and the mirror unit 25 can be brought close to each other, and the optical waveguide 23 and the optical element 26 can be optically coupled with low loss.

  The substrate 21, the electrode part 22, the first cladding layer 23a, the solder resist layer 24, the core part 23b, and the second cladding layer 23c are respectively the substrate 1, the electrode part 2, and the second part of the optoelectric wiring board 100 of the first embodiment. The same thing as 1 clad layer 3a, soldering resist layer 4, core part 3b, and 2nd clad layer 3c can be used. Moreover, the manufacturing method of the opto-electric wiring board 200 can be the same manufacturing method as that of the opto-electric wiring board 100.

1, 21: Substrate 1a, 21a: First surface 2, 22: Electrode portion 2a, 22a: Second surface 3a, 23a: First cladding layer 3aa, 23aa: Third surface 3A, 23A: End portions 3b, 23b: Core portions 3c, 33c: second clad layer 6, 26: optical element 7, 27: connecting member 100, 200: optoelectric wiring board 101, 201: electronic device

Claims (9)

A substrate having a first surface;
An electrode portion disposed on the first surface and having a second surface opposite to the substrate;
A first cladding layer disposed on the first surface so as to expose the second surface, and having a third surface opposite to the substrate;
A solder resist layer disposed from the second surface to the end of the third surface;
A core portion disposed on a portion of the third surface whose distance from the second surface is farther than the end portion;
An optoelectric wiring board comprising a second cladding layer covering the core part.   The optoelectric wiring board according to claim 1, wherein the first cladding layer is separated from the electrode portion.   The optoelectric wiring board according to claim 1, wherein the first cladding layer is in contact with the electrode portion.   The optoelectric wiring board according to claim 1, wherein the first cladding layer surrounds the electrode portion when viewed in plan.   The optoelectric wiring board according to claim 4, wherein a portion where the solder resist layer and the first cladding layer overlap each other surrounds the electrode portion. An optoelectric wiring board according to any one of claims 1 to 5,
An electronic device comprising: an optical element connected to the second surface via a connection member. Preparing a substrate having a first surface;
Providing an electrode portion having a second surface opposite to the substrate on the first surface;
Providing a first cladding layer having a third surface opposite to the substrate on the first surface so that the second surface is exposed;
Providing a solder resist layer from the second surface to the end of the third surface;
And a step of providing a core portion and a second cladding layer covering the core portion on a portion of the third surface that is farther from the end portion than the end portion.   The method of manufacturing an optoelectric wiring board according to claim 7, wherein the step of providing the core portion and the second cladding layer is performed after the step of providing the solder resist layer.   The method of manufacturing an optoelectric wiring board according to claim 7, wherein the step of providing the solder resist layer is performed after the step of providing the core portion and the second cladding layer.